This super moist dark chocolate mousse cake combines unsweetened natural cocoa powder and dark cocoa powder for an extra rich flavor. Fill the cake with a simplified chocolate mousse and cover the whole dessert with semi-sweet chocolate ganache. If needed, you can prepare the ganache and mousse ahead of time.
My s’mores chocolate mousse inspired me to play around in the kitchen the other week. I’ve always loved chocolate mousse, back to my childhood when my mom served it as an easy (yet totally elegant) dessert on the holiday table. Chocolate mousse is simple divinity in its own right, but when paired with chocolate cake, it’s downright decadent.
I made this chocolate mousse cake for my husband Kevin’s birthday. This cake basically demands a huge gathering because– trust me– you don’t want to be left alone with its temptation. It WILL call out your name each time you open the refrigerator.
3 Parts to Dark Chocolate Mousse Cake
Let’s break down each component of this intensely rich cake:
- Dark Chocolate Cake: This is actually a variation of my tuxedo cake, which originated from my chocolate cake recipe. In recent years, I’ve found that replacing sour cream for some of the buttermilk gives the cake more structure.
- Chocolate Mousse: I researched simplified ways to make a fluffy chocolate mousse filling without the use of eggs or gelatin. This chocolate mousse filling combines real chocolate and homemade whipped cream. Or our whipped frosting would make a wonderful alternative filling if you don’t want to make the chocolate mousse!
- Chocolate Ganache: Top the whole cake with 2 ingredient semi-sweet chocolate ganache. You should be a chocolate ganache pro by now!
Video Tutorial: Chocolate Mousse Cake
Stick-to-the-back-of-your-fork moist. This is every chocolate lover’s dream!
Dark Chocolate Cake
Use this chocolate cake as the starting point. For a sturdier, yet moister crumb, swap some sour cream in for the buttermilk and reduce the hot liquid. The acidity in both sour cream and buttermilk is a must to properly leaven this cake. (If desired, see baking powder vs baking soda for more information.) This cake has a natural dark chocolate taste, but to deepen that flavor, use a mix of natural cocoa and Hershey’s Special Dark cocoa powder. A touch of espresso powder and hot coffee further enhances the chocolate flavor. The cake will not taste like coffee– rather, the two add depth to the cake’s chocolate flavor.
- Why hot liquid? The hot liquid encourages the cocoa powder to bloom and dissolve. If you don’t drink coffee, you can use hot water.
You have options! You can make this cake into 2, 3, or 4 layers. I highly recommend 3 or 4 layers because there’s over 4 cups of chocolate mousse to spread inside. You can use 8 inch or 9 inch pans. The bake times are similar, see recipe notes.
A cup of chocolate chips adds even more chocolate flavor. I used 1 cup (180g) of mini semi-sweet chocolate chips in this pictured cake, but left them out in the video. They’re optional– but definitely worth the addition!!
You can also see this exact cake batter baked as three layers in both my chocolate peanut butter cake and chocolate raspberry cake (try one of those next!).
Simplified Chocolate Mousse
The chocolate mousse adds a creamy and light contrast to the dark chocolate layers. You need 6 ingredients:
- Hot Water
- Cocoa Powder – natural or dutch-process
- Melted Chocolate – use two 4-ounce chocolate baking bars found in the baking aisle
- Heavy Cream
- Confectioners’ Sugar
- Vanilla Extract
Whisk the hot water and cocoa powder together. Pour into melted chocolate. The hot water breaks up the chocolate, adding to the airy mousse consistency. Cocoa powder creates additional chocolate flavor. Fold this chocolate mixture into whipped cream– a combination of heavy cream, confectioners’ sugar, and vanilla extract.
Whipped cream + our chocolate mixture. ↑
Fold them together to make our chocolate mousse filling. ↓
Baker’s Tip: The chocolate mousse must chill in the refrigerator before using, so it’s a good idea to make it ahead of time or as the chocolate cake layers are cooling. The mousse is best cold, so I actually recommend serving the cake cold. (Additionally, the cake is much easier to assemble if the mousse is cold!)
I won’t go into a lot of detail about the chocolate ganache because I have a complete chocolate ganache tutorial for you! Like the chocolate mousse, it’s imperative to use pure chocolate. Wait about 20 minutes for the ganache to thicken before pouring onto the cake.
How to Assemble & Decorate Chocolate Mousse Cake
Chocolate ganache enrobes 4 cake layers and 3 mousse layers. Place bottom cake layer on your cake stand or serving plate. Using a large icing spatula, evenly cover the top with about 1.5 cups of chilled chocolate mousse. Top with 2nd cake layer and another 1.5 cups of mousse. Top with the third cake layer, then spread another 1.5 cups mousse evenly on top. (Save a large spoonful of mousse for a thin crumb coat.) Top with final 4th cake layer. Spread any remaining mousse around the sides as a crumb coat. Run a bench scraper around the cake to smooth it out. Refrigerate cake for at least 1 hour and up to 4 hours. Chocolate mousse is pretty fluffy, so the cake won’t hold its shape unless it’s properly chilled.
Pour ganache on top then run a bench scraper around the sides to smooth it out. You can serve the cake immediately or wait for the chocolate ganache to set. 🙂
What About Cupcakes?
Instead of a big cake, you can make chocolate mousse cupcakes. Use my chocolate cupcakes recipe and halve the chocolate mousse and chocolate ganache recipes below. Fill the cupcakes with chocolate mousse using my Sugar Plum Fairy Cupcakes as an example. Drizzle cooled cupcakes with ganache. Eat your heart out!
More Indulgent Chocolate Desserts
- Dark Chocolate Bread Pudding
- German Chocolate Cake
- Flourless Chocolate Cake
- Black Forest Cake
- Chocolate Lava Cakes
- Chocolate Mousse Pie
- Mint Chocolate Cake
Dark Chocolate Mousse Cake
- Prep Time: 2 hours, 30 minutes (includes chilling)
- Cook Time: 25 minutes
- Total Time: 5 hours, 55 minutes (includes cooling)
- Yield: serves 12
- Category: Cake
- Method: Baking
- Cuisine: American
This super moist dark chocolate cake combines unsweetened natural cocoa powder and dark cocoa powder for an extra rich flavor. Fill the cake with a simplified chocolate mousse and cover it with semi-sweet chocolate ganache. If needed, you can prepare the ganache and mousse ahead of time. See notes.
- 1 and 3/4 cups (219g) all-purpose flour (spoon & leveled)
- 3/4 cup (62g) unsweetened natural cocoa powder* (see note)
- 1 and 3/4 cups (350g) granulated sugar
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon salt
- 2 teaspoons espresso powder (optional)*
- 1/2 cup (120ml) canola or vegetable oil
- 2 large eggs, at room temperature
- 3/4 cup (180g) full fat sour cream, at room temperature
- 1/2 cup (120ml) buttermilk, at room temperature*
- 2 teaspoons pure vanilla extract
- 1/2 cup (120ml) hot water or coffee*
- optional: 1 cup (180g) mini or regular semi-sweet chocolate chips
- optional garnish: fresh berries and/or chocolate shavings
- 1/2 cup (120ml) hot water
- 1/4 cup (22g) unsweetened cocoa powder* (see note)
- two 4-ounce quality semi-sweet chocolate bars (113g each), finely chopped*
- 2 cups (480ml) heavy cream or heavy whipping cream
- 2 Tablespoons (15g) confectioners’ sugar
- 1/2 teaspoon pure vanilla extract
- two 4-ounce quality semi-sweet chocolate bars (113g each), finely chopped*
- 1 cup (240ml) heavy cream or heavy whipping cream
- Preheat oven to 350°F (177°C). Grease four 8-inch or 9-inch cake pans, line with parchment paper rounds, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans. (If it’s helpful, see this parchment paper rounds for cakes video & post.)
- Make the cake: Whisk the flour, cocoa powder, sugar, baking soda, baking powder, salt, and espresso powder (if using) together in a large bowl. Set aside. Using a handheld or stand mixer fitted with a whisk attachment (or you can use a whisk) mix the oil, eggs, and sour cream together on medium-high speed until combined. Add the buttermilk and vanilla and mix until combined. Pour the wet ingredients into the dry ingredients, add the hot water/coffee, and whisk or beat on low speed until the batter is completely combined. Fold in the chocolate chips, if using.
- Divide batter evenly between 4 pans. Bake for 19-23 minutes. Baking times vary, so keep an eye on yours. The cakes are done when a toothpick inserted in the center comes out clean.
- Remove the cakes from the oven and set on a wire rack. Allow to cool completely in the pan. The cakes may slightly sink in the middle as they cool—that’s expected.
- As the cakes cool, prepare the chocolate mousse so it can chill and be ready at the same time as the cake layers. You can also prepare the mousse 1-2 days ahead of time. Whisk the hot water and cocoa powder together. Set aside. Melt the chopped chocolate bars in a double boiler or use the microwave. If using the microwave: place the chopped chocolate in a medium heat-proof bowl. Melt in 20 second increments in the microwave, stirring after each increment until completely melted and smooth. Pour hot water/cocoa mixture into melted chocolate and stir until thick and smooth. Set aside. Using a hand mixer or a stand mixer fitted with a whisk attachment, whip the heavy cream, confectioners’ sugar, and vanilla extract together on medium-high speed until medium peaks form, about 3-4 minutes. Medium peaks are between soft/loose peaks and stiff peaks. Pour in the chocolate mixture and using a spoon or rubber spatula, gently fold together. Avoid over-mixing which can deflate/thin out the mousse. Cover mousse and chill in the refrigerator for at least 2 hours and up to 2 days. Makes about 4.5 cups chocolate mousse.
- Assemble layers before preparing chocolate ganache: First, level the cakes if needed: using a large serrated knife, slice a thin layer off the tops of the cakes to create a flat surface. Discard (or crumble over ice cream!). Place 1 cake layer on your cake stand or serving plate. Using a large icing spatula, evenly cover the top with about 1.5 cups chocolate mousse. Top with 2nd layer and evenly cover the top with 1.5 cups chocolate mousse. Top with the third cake layer, then spread another 1.5 cups mousse evenly on top. Save a large spoonful of mousse for a thin crumb coat. Top with final 4th cake layer. Spread any remaining mousse around the sides as a crumb coat. Run a bench scraper around the cake to smooth out crumb coat. Refrigerate cake for at least 1 hour and up to 4 hours. Prepare the ganache as you wait.
- Chocolate Ganache: Place chopped chocolate in a medium heat-proof bowl. Heat the cream in a small saucepan over medium heat until it begins to gently simmer. (Do not let it come to a rapid boil– that’s too hot!) Pour over chocolate, then let it sit for 2-3 minutes to gently soften the chocolate. With a metal spoon or small rubber spatula, very slowly stir until chocolate has melted and mixture is smooth. The finer you chopped the chocolate, the quicker it will melt with the cream. If it’s not melting, do not microwave it. If needed, see Troubleshooting Chocolate Ganache. Once ganache mixture is smooth, let it cool for 20 minutes at room temperature before spreading on chilled cake.
- Pour/spoon ganache on chilled cake. Smooth the top with an icing spatula and the sides with a bench scraper. Top with optional garnish such as fresh berries and/or chocolate shavings. Serve cake immediately or chill, uncovered, for up to 4-6 hours before serving. Cake can be served at room temperature or chilled.
- Cover leftover cake tightly and store in the refrigerator for 5 days.
- Make Ahead & Freezing Instructions: Prepare cake through step 4. Wrap the individual baked and cooled cake layers tightly and refrigerate for up to 2 days or freeze up to 3 months. Bring to room temperature, make mousse filling, then continue with step 6. You can prepare the chocolate mousse in advance. See step 5. You can also prepare the chocolate ganache ahead of time too. Refrigerate prepared ganache for up to 2-3 days. Bring to room temperature before spreading onto cake. Frosted cake freezes well, up to 3 months. Thaw overnight in the refrigerator, then bring to room temperature or serve cold.
- 3 Layer Cake: You can also prepare this cake as a 3 layer cake. Divide batter between three 8-inch or 9-inch cake pans in step 1 and bake for 22-25 minutes or until a toothpick inserted in the center comes out clean. Use about 2 cups of chocolate mousse between each layer.
- Espresso Powder/Coffee: Espresso powder and coffee will not make the cake taste like coffee. Rather, they deepen the chocolate flavor. I highly recommend them both. If coffee isn’t your thing, you can leave out the espresso powder and use extra hot water instead of the hot coffee.
- Cocoa Powder: For the best dark chocolate flavor in the cake, I recommend using a blend of unsweetened natural cocoa powder (1/4 cup; 22g) and Hershey’s “Special Dark” cocoa powder (1/2 cup; 43g). Hershey’s Special Dark is actually a mix of natural cocoa powder (an acid) and dutch-process cocoa powder (a base) and it worked fine in this recipe. This recipe needs acidic natural cocoa powder, so do not use ALL dutch-process cocoa powder. For best results, use 3/4 cup (65g) natural or the blend of natural/Special Dark I used. For the chocolate mousse, you can use either unsweetened natural or dutch-process cocoa powder. (Or the Hershey’s Special Dark.)
- Why Room Temperature? All refrigerated items should be at room temperature so the batter mixes together easily and evenly. Read more about why room temperature ingredients are important. Instead of sour cream, you can use plain yogurt. The cake won’t taste as rich, but it’s a fine substitute.
- Buttermilk: Buttermilk is required for this recipe. You can make your own DIY version of buttermilk if needed. Add 1 teaspoon of white vinegar or lemon juice to a liquid measuring cup. Then add enough whole milk to the same measuring cup until it reaches 1/2 cup. (In a pinch, lower fat or nondairy milks work for this soured milk, but the cake won’t taste as moist or rich.) Stir it around and let sit for 5 minutes. The homemade “buttermilk” will be somewhat curdled and ready to use in the recipe.
- Chocolate in Mousse & Ganache: Mousse & ganache will only set if the correct chocolate is used. You can use high quality chocolate chips if needed (I prefer Ghirardelli semi-sweet chocolate chips), but I recommend using pure chocolate baking bars. You can find them right next to the chocolate chips in the baking aisle. They are sold in 4 ounce bars. I like Bakers or Ghirardelli brands.
Keywords: cake, chocolate mousse, dark chocolate
Reader Comments & Reviews
As with so many of your recipes this was just fabulous! Where did you get the cake sband I would really like to have one.
Hi Becky, thanks so much! The cake stand is from Sur La Table. The exact one is linked in our Gift Guide under “Carriers, Cake Stands, & Serveware.”
Help! My mousse “seized” for some reason. When I added the chocolate mixture to the whipped cream, the chocolate immediately hardened and created big clumps throughout my mousse. What did I do wrong?? I let the chocolate mixture cool to about room temp before adding it to the whipped cream. Maybe my whipping cream was too cold??
Hi Abbie, you don’t want the chocolate mixture to cool that long. It should really only be set aside for a few minutes as you whip the cream. So, it will still be a bit warm when you fold into the whipped cream mixture. I wonder if yours cooled too long, and solidified.
This cake is top notch! It is not too rich or sweet, just perfect. It will be my new go-to cake for chocolate lovers.
Can I use chocolate chips instead of the chocolate bars. If so, how much chips should I use?
Hi Lori, Mousse & ganache will only set if the correct chocolate is used. You can use the same amount of high quality chocolate chips if needed (we prefer Ghirardelli semi-sweet chocolate chips), but we recommend using pure chocolate baking bars. You can find them right next to the chocolate chips in the baking aisle. They are sold in 4 ounce bars. We like Bakers or Ghirardelli brands.
This recipe was absolutely delicious–the best chocolate cake I’ve ever had. The contrast between the sweet mousse and bittersweet layers and ganache was amazing. I never adapt your recipes, but for our anniversary we wanted a raspberry-chocolate mousse cake, so I spread a very thin layer of raspberry preserves on each layer before adding the mousse. Your recipes are wonderful and your directions are so clear and thorough, it’s a pleasure to bake them. Can’t wait to make this one again!
I love so many recipes from your site and you’ve never steered me wrong! However, I erroneously mixed the sugar into the whip cream before whipping and could never get it to form peaks. I had to throw out the ruined whip cream and start over. I whip cream all the time, and have only had this to happen to me one other time!
This cake is a hit. I’m from Germany, and for some recipes it’s not always easy to get just the correct ingredient for the recipe. But this was so easy to make, assemble and then -the taste!! I made it as a gift for a friend and got so many compliments and requests for the recipe!!
I can’t really express how much your cookies, cakes, bars etc. ecipes enrich my world, Sally! I tried many and even when they did not always turn out as they would have if I had the american product to use (and there would’ve been a difference), I am always happy with the result.
An alltime runner here are the bite-size M&M pretzel cookies. My sons friend requests them for his birthday every year, they are his absolute favourite.
I learned so much about temperatures, ingredients, texture – thanks for taking all the time to explain which influence it has on the outcome.
My friends and family request this one so much now that I’m starting to miss baking other kinds of cakes!!! But there’s a reason it’s requested so much. It’s a great recipe. As decadent as described—a small piece goes a long way. Sometimes I just make the mousse on its own with a garnish of fresh raspberries because it’s so simple and a fun alternative to baked desserts.
I have Dutch process cocoa powder and black onyx cocoa powder that I purchased from a local specialty spice shop. May I use those in the cake instead of the Hershey’s powder you recommend or should I just stick with the Hershey’s powder? If I can use my powder, what ratios for the two powders do you recommend? Thanks.
Hi Tim, Unfortunately, this recipe needs acidic natural cocoa powder, so do not use ALL dutch-process cocoa powder. It would take some recipe testing to tweak it so that you can use all Dutch-process and still get great results. You can learn more about the difference between the two here. If you decide to do any experimenting, we’d love to know how it turns out for you — sorry we can’t help more!
Just thought I’d mention: I use Dutch-process cocoa every time I bake this cake (which has been at least three or four times now!) and it always turns out beautifully. I’ve never noticed any issues with the texture, flavor, rise…it’s moist, rich, and tastes delicious! I always use Rodelle Dutch-process because it’s what I have on hand, and I have personally never had a problem with it
Hi! My family members do not like really sweet cakes, weird hey?!
If I reduce the sugar to 3/4 cups, will it affect the consistency of the cake?
Thanks for your amazing recipes and your help!
Hi Fannie, This cake is still pretty sweet, but you can use unsweetened chocolate in the mousse and even *slightly* reduce the sugar in the cake to 1 and 1/2 cups. (300g)
My daughter requested this for her Sweet 16. Can I use semi sweet chocolate baking wafers for the mousse/ganache?
Hi Bev, for the best results, we highly recommend sticking with pure baking chocolate bars here. Baking wafers, even the high quality type, may prevent the mousse and ganache from setting up properly. Hope the cake is a hit for your daughter’s birthday!
I just made this cake for my coworker’s birthday and everyone loved it. It took me a while since I’m not a seasoned baker and I learned as I went. Fortunately I made two cakes so the second one came out a little better, but when the mousse was at room temperature too long it began to melt in the heat of the kitchen lol…Thanks for sharing, it was delicious!
I made this for a special Occassion and got so many compliments! It is a moist, rich chocolate flavor that’s not too sweet. This is definitely a keeper and presents so well for a special occasion!
Hi Sally! Love, love, love your work, so thanks up front! Would it be possible to add a bit of raspberry compote under the mousse as an added filling or would that mess with the mousse? Best.
Hi Andrea, we haven’t tested the recipe this way, but it does sound delicious! If you give it a try, please let us know how it turns out.
This recipe is great and easy to follow. The cake is so good but to me the mousse is a tad too bitter, can i just add a table spoon or more sugar to help combat this in the future?
Hi Ronda, yes, you can try adding an extra Tablespoon of sugar to sweeten the mousse a bit more to your taste. You could also try using a different chocolate in it, one with a lower percentage of cacao. 56% is considered semi-sweet, while 60% is bittersweet. Hope you enjoy!
Hi Sally, thank you so much for this recipe! I’m very excited to try it out as many of your other recipes have been huge hits with my family :D. One question: can I freeze the entire cake after the ganache layer? I’d like to coat the cake with a mirror glaze if possible.
Hi Tiffany, Frosted cake freezes well, up to 3 months. Thaw overnight in the refrigerator, then bring to room temperature or serve cold.
Hi, I love this recipe and make it for special occasions and it’s always a huge hit. I was thinking of making it for my sons birthday and carving it into a number cake and using marshmallow buttercream instead topped with sweets. Do you think that would work and taste okay?
Hi Juliet, you can make this recipe as a 9×13 sheet cake (same oven temperature, about 35-40 minutes bake time). The cake itself should hold up cut into a number or letter but we haven’t tested it, and it would be delicious with marshmallow meringue. Let us know if you give it a try!
This looks delicious. I wanted to use fondant instead of ganache. Would this work? Would I still use the mousse as a crumb coating or should I use buttercream instead? Thanks so much!
Hi Kate, this cake should hold up fine under fondant, but fondant covered cakes should not be stored in the fridge. So glad you love this cake!
Hi Sally, can this cake be fully assembled and put in the fridge until it is served the next day?
Hi Jenn, sure can! Enjoy.
I am about to attempt this cake for my parent’s anniversary! Had a question before I try though-My dad absolutely hates the taste of baking soda in his chocolate cakes. Is the baking soda perceptible in this one? In your opinion do you think it would be fine if I just used 1.5 baking soda along with the baking powder?
Hi Dana, We’ve never been able to taste the baking soda in this recipe – it’s so chocolatey!! You can try reducing the baking soda a bit but keep in mind the cake may not rise as much causing it to be more dense. We hope your parents have a happy anniversary!
The cake flavor was good, but I think would be best enjoyed with some vanilla icecream to counter the richness of the chocolate. It’s almost unbearably chocolatey. The cake was also super unstable because the second you take it out of the fridge, the mousse begins to melt out of the layers.
This is my go to chocolate cake recipe!! Love the mousse too. I did a 1.5x recipe of the mousse and have a bit of extra, whats the best way of storing it for future use?
Hi Kris! It will only hold its texture for a few days. We don’t recommend freezing.
This is a brilliant cake for a celebration as it’s really impressive. The chocolate mousse makes it feel very decadent but it’s not sickly. I have never had so many compliments on a cake. When I made it for children I skipped the ganache coating and just covered the mousse coating in flaked chocolate.
Hi sally! Would this mousse filling hold up in a two tier cake? Thank ykh
Hi Zarah, we haven’t tested it. You would certainly need proper supports for a tiered cake. We also don’t recommend using this chocolate cake recipe as a bottom tier as it isn’t sturdy enough. You can read more about our recommendations for tiered cakes in this homemade wedding cake post.
Can I make this recipe using two 6-inch cake pans?
Hi Nicole! This would be too much batter for two 6 inch cake pans. We recommend using this chocolate cupcakes recipe as the batter to make a 3 layer 6 inch cake. See our 6 inch cake recipes post as a guide. Halve the chocolate mousse and ganache from this recipe so there’s just enough. Hope this helps!
would it work for 4, 6 inch rounds? this recipe sounds more rich with the coffee than the cupcake recipe?
It will be a bit too much batter for 4, 6 inch rounds, but you could fill your 4 pans half way, then use any leftover batter for a few cupcakes on the side. Enjoy!
Can this cake be made into a spherical cake (soccer ball)? I have the wilton ball cake pans. What would be the temp and baking time? Also, can this cake handle being covered by fondant?
I loved this cake so much and its stunning with taste, fluffy, moist !!! This should be a to-go recipe for all chocolate lovers !! This time I have made for one of my friend’s B’day . Thank you so much for sharing the recipe.
I grew up with a Mom who was a phenomenal cook and baker…a perfectionist! I was spoiled that way.
This is the BEST chocolate cake I’ve ever made/tasted! The velvety texture and taste are perfect! Thank you for sharing your recipe with me!
We had friends over for a game night and I made this cake and it was a huge hit! Chocolate mousse cake is the cake I request when it’s my birthday and this was my first attempt at making it myself. Turned out fantastic. I made 4 layers with 8” pans. I keep my cocoa powder in a clear canister so I had no idea what kind it was – I just used what I had and everything was delicious. This might be my favorite recipe ever.
I wish I could rate the cake and the mousse separately! I’d give the cake 5 stars. It’s rich and moist with a delicate crumb.
The mousse I cannot recommend. I’d give it 2 stars. It’s fluffy and the texture is good, but the flavor is all wrong. I think it’s the cocoa powder/water. The mousse doesn’t taste like mousse. It has a watery/bland flavor and the cocoa powder is doing nothing for it.
I agree about the mousse being good but not quite up to par. Otherwise, I cut the sugar in the cake and used dark chocolate dipping bars from our local high end candy company and had great success with the overall flavor not being too sweet and perfectly complimented by fresh strawberries.