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
Is there a variation I can use cake flour with? I’m trying to get rid of a box.
Hi Kat, This cake already has cocoa powder— which is a VERY fine dry ingredient. The combination of cake flour and cocoa powder usually results in a flimsy cake.
I have so many other cakes that call for cake flour, I’m sure you will find a way to use up your box! Here they all are: https://sallysbakingaddiction.com/tag/cake-flour/
Oh my my! This chocolate cake is so delicious. My first attempt isn’t so pretty but it tastes amazing. I tried pre-making the ganache but it was too hard to spread over after being refrigerated & never quite soft enough again after sitting out for awhile so I quickly & easily made another batch to pour over. Thanks to another review I found out about using powdered buttermilk which is so handy for baking.
Absolutely the most tasty and moist chocolate cake I have ever made. I have been baking your recipes for a long time and they never fail. Thanks.
I made this last weekend over the course of two days. The cake was delicious and very rich, I loved the deep chocolate flavor! Your recipes never disappoint!
Such a rich, decadent, moist cake! The combination of dark chocolate and coffee is amazing! I added espresso powder to the ganache and used espresso morsels in the cake batter to give it an added depth of flavors. I also made it in three layers. Love, love, love this recipe!
Such a beautiful and delicious cake! Super chocolatey and not too sweet, the best! Leftovers were eaten for breakfast standing in front of fridge. With a fork because I’m ladylike.
Hi, I would love to know whether I could bake in a 8″ pan and sliced into 3layer as I only have one 8″ springform tray.
Thank you! Love your recipe!
I made 1/2 of this recipe for my husband’s birthday cake. Baked in a 8*8 pan, cut in half and stacked layers. On the bottom before I baked I had made a pecan praline mix. Then frosted with sweetened whipped cream. It was amazing. Another great recipe Sally. Thanks!
The mousse turned out far too thin to be spread on the cake! Admittedly, I refrigerated it for the minimum 2 hours. How can I thicken it?!
Hi Michael, When you whipped cream, sugar, and vanilla together did you get it to reach medium peaks? Then when you combine this whipped mixture with the chocolate be careful to very gently fold them together. Over-mixing at this step will deflate/thin out the mousse.
What modifications do I need to do to the mousse and ganache to make this as 2 layer cake?
Hi Amu! I recommend halving the mousse. Having the ganache should be enough too but you can try 6 ounces chocolate and 3/4 cup heavy cream just to be sure there’s enough!
Hi Sally! I made 2 of your cake recipes for a joint birthday party and they were delicious! Thank you! I am making this one for my other daughter’s birthday party in 2 weeks. I did read about freezing recommendations but I just want to make sure I get it right. You don’t recommend freezing the whole cake with the mouse and ganache, correct? I froze the other ones but they didn’t have mousse and ganache. It helps me a lot to freeze ahead of time because I do all the food for our parties. Thank you!
Hi Jill, The frosted cake freezes well also, up to 3 months! Thaw overnight in the refrigerator, then bring to room temperature or serve cold. Enjoy!
I am worried that the ganache will turn hard once it is refrigerated and will be difficult to cut clean slices and that the ganache will crack and crumble.
It will get thicker but it will never solidify to the point of cracking.
This cake was delicious! I used bittersweet chocolate for the mousse, but semisweet for the ganache. It came out perfectly. Intense chocolate flavor and definitely not too sweet. It was definitely a crowd pleaser!
Hi Sally! Looking forward to making this cake for family this weekend. I have King Arthur flour double Dutch dark cocoa in my arsenal. Can I use that in place of Hershey special dark cocoa powder? Thanks. As always. Your the best!!!
Hi Rosemarie, You can use the King Arthur dutch cocoa instead of the Hershey’s special dark. 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.
I am making this cake with the information and the products needed and will be making this (hopefully done right) and will make it close to 3 of my friends party on 8/25/19. I am honored to make it.
Made this using the combination of Special Dark cocoa and regular cocoa that Sally recommends and it turned out perfect! Filled it and covered it with peanut butter frosting and then did a dark chocolate ganache drip. It was awesome!!
I made this in 3, 8” layers and followed Sally’s time recommendation and it was perfect.
With this cake and Sally’s triple chocolate, I replace about 1/3 of the cocoa with KAF’s Black Cocoa and I am a fan of the results. The mousse is excellent.
Thoughts on converting to 6 inch pans?
Hi Carolyn! I recommend using my chocolate cupcakes recipe as the batter to make a 3 layer 6 inch cake. See my 6 inch cake recipes as a guide. Halve the chocolate mousse and ganache so there’s just enough.
Very good cake! So simple and delicious! Will make again for my mom’s birthday since she loves that dark, rich chocolate taste!
Made this today for a birthday and it turned out really great! Moist, chocolatey and delicious. It was certainly rich, but that didn’t stop us from going back for seconds! Thanks for another great recipe Sally – this one is a keeper!
Hi Sally – this looks like the perfect cake for me to bake for my daughter’s birthday this weekend! Do you assemble it on a cake board, then transfer it to the stand?
What brand of chocolate do you recommend for the semi-sweet chocolate bars for the ganache? I am having a large crowd for a cookout this weekend and 5 birthdays to celebrate, and this cake looks like the perfect choice!
Hi Susan, I use any pure chocolate baking bar, such as Bakers or Ghirardelli brands. I hope the cake is a hit!
Hi Sally, I am a great fan of yours. I have tried lots of your recipes. I bake only with your recipes!!! I am planning to bake this for my husband’s birthday. We are just 4 and this cake is too big for us. Can I half the recipe and bake it in 6 inch cake pans? Can I have the recipe for the mousse and ganache as well? Please let me know. Thank you!!
Hi Vidhya, 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!
Super prepared!! Love it! 🙂
Can this be made in a 9X 13, with a layer of mousse on top of a layer of cake, and frozen?
I can’t see why not! This batter bakes in about 40 minutes in a 9×13 inch cake pan. Same oven temperature.
Hi Sally, this dark chocolate cake looks gorgeous. I’m not a baker, but love to bake once in a while. My question is regarding chocolate mouse. Do you have to wait for the melted chocolate to cool completely before mixing is with the whip cream?
Great question. No need to let it cool, though you certainly could! I always mix it right into the whipped cream.
What kind of Buttermilk do you all use? I’m not really much of a baker and every time a recipe calls for buttermilk, I never know if I should buy can or the Cultured Buttermilk where the regular milk is. I tried doing the Whole Milk/vinegar before, but I don’t think that it turned out right. Any suggestions on what kind to get? Thanks
Cultured buttermilk is actually what you want – it’s how it’s sold in stores in the U.S. I have heard from many other bakers that they use the powdered buttermilk sold in the baking aisle that you mix with water and they all say that works well also!
Your chocolate cakes and cupcakes are divine. Several cakes have given relatives that I am one hell of a baker. I say, don’t give me any credit, it’s that Maryland girl.
I can only imagine this cake will be even better. Is that is even possible? Thank you so much.
Hey Sally! I simply couldn’t resist making this right away…..the combo of cake, mousse and ganache is ultimate indulgence!! Unfortunately, my chocolate cakes sank in the middle…..any tips/advice to avoid this next time? The mousse turned out perfect! Waiting for the cakes to cool now. Thanks, Nona
Hi Nona! Over-filling the cake pans or under-baking the cakes will result in sinking in the center. Were they baked all the way through? Love this mousse!
Hi Sally. I have only 2 8” pans. Could I bake 2 first then 2 afterwards? Would the batter be okay?
Yes, it should be fine!
Oh Sally, I really want to make this cake…….like now. I’m totally salivating. But there’s one small problem- my daughter is on a red eye and I have to get her in two hours! That, and I spent the day baking your honey oatmeal bread, cheese crackers, and brownies. However, I simply must make this before she goes back to Denver, but I’m going to halve the recipe. As much as we’re chocoholics, (like mother, like daughter!), I don’t think we’ll be able to power through a whole cake, even with her teenage brother’s help! Me thinks after making this, she just might want to move back home, LOL! I’ll report back how it turns out!
P.S. I cut the cheese crackers in animal shapes…turtles, ducks, and they are really cute! The leftover dough stayed in the fridge for 5 days and tasted just as good as the batch I baked on day one. They are highly addictive and my boys loved them!
I hope you have a great visit with your daughter!! What a delicious dessert to make for your family 🙂 Your cheese crackers in animal shapes sound absolutely adorable!! Such a fun idea! Happy baking!
This chocolate mousse cake is simply gorgeous! I love those layers – so pretty ♥