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.
Taunting you.
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!)
Chocolate Ganache
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!
You can also use the chocolate mousse instead of pastry cream in homemade mille-feuille!
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
Description
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.
Ingredients
- 1 and 3/4 cups (219g) all-purpose flour (spooned & 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
Chocolate Mousse
- 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
Chocolate Ganache
- two 4-ounce quality semi-sweet chocolate bars (113g each), finely chopped*
- 1 cup (240ml) heavy cream or heavy whipping cream
Instructions
- 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, cake turntable, 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.
Notes
- 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.
- Special Tools (affiliate links): 8-inch Round Cake Pans or 9-inch Round Cake Pans | Glass Mixing Bowl | Whisk | Electric Mixer (Handheld or Stand) | Cooling Rack | Double Boiler | Cake Stand or Cake Turntable | Large Icing Spatula | Bench Scraper | Cake Carrier (for storage)
- 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.
I made this cake today for my daughter’s birthday with one edit, I added a raspberry couli I made from fresh berries, honey, cognac and lemon juice in the center of the mousse filling. It was an absolute success!!! Thank you so much for all of the fantastic recipes.
Hi Sally , do you think if I add an extra two cake layers( this recipe) on top it would hold well ? Thank you
Hi Aneta, I just responded to your comment on our Triple Chocolate Cake post. We don’t have a sturdy enough chocolate cake to support a second tier at this time!
Hi Sally,
I made this cake at the weekend as a birthday cake. We did 4 layers and used dark chocolate at 70% where we could. (Dark chocolate and a peaty whisky go so well together!!)
Simply stated, this is the best chocolate cake we have ever made (or bought!).
It was moist, rich and absolutely delicious.
Thank you
Brian
When you say to use pure chocolate what exactly do you mean? A 70% bakers chocolate?
Hi Dan! You can find pure chocolate baking bars right next to the chocolate chips in the baking aisle. They are sold in 4 ounce bars. We like Bakers or Ghirardelli brands. We use semi sweet which is about 56% cocoa. 70% would also work for a richer chocolate flavor!
Hi Sally,
I am absolutely itching to make this recipe for my birthday in a few days… however, I have searched high and low for places that sell natural cocoa powder and I cannot find it anywhere! I live in New Zealand and most of the cocoa powders that are sold in grocery stores are dutch-processed. I know that natural cocoa powder is necessary in this recipe for its acidity, but I was wondering if I could use dutch-process instead and add another acidic ingredient, such as substituting some of the white sugar for brown sugar? I was also wanting to make the sour cream version, so would adding sour cream make up for the lack of acidity from the natural cocoa powder?
This recipe looks incredible and I would love to find a solution to my cocoa powder conundrum so that I can try it myself.
I love your blog by the way! You have taught me so much 🙂
Thanks,
Paige
Hi Paige! Thank you so much for your kind note and for making and trusting our recipes. 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!
Sure!
can i use this on your marble cake instead of chocolate cake base?
Definitely!
Hi Sally, I have made this cake multiple times and it is SO good. I’m wondering if it would work in 3 square pans (10″, 8″ and 6″ ) then stacked on top of one another?
Thanks so much!!
Hi Seren! Here is everything you need to know about converting recipes to different Cake Pan Sizes.
Hi Trina,
Thanks so much! I guess I was more wondering if the cakes would be stable enough to hold one another?
Hi Sally! I love all of your recipes that I have tried so far – thank you so much! I’m wondering whether you’ve ever tried combining your black forest cake with this cake? Do you think you could successfully add the cherry syrup portion from the black forest cake to this one? Thank you!
Hi Lisa, we haven’t tried it but we can’t see why that wouldn’t work. Let us know if you give it a go!
Hi Sally! I’ve made this cake a million times and it’s my absolute favorite!
Do you think this cake could be made with Nutella mousse, and if so is there a Nutella mousse recipe that you could recommend?
Hi Anisa, a Nutella mousse would be delicious! You can try with the mousse filling from these homemade eclairs (swapping the peanut butter for Nutella).
I am making this for my mother’s birthday this week and it looks amazing! Do you think the cake will be okay if I make 2 8in rounds and then divide each cake into 2? I know I’ll have to bake them longer, just wondering if the crumb is strong enough to withstand me cutting them. I bought the Wilton cake leveler and I’m excited to see how it works. Thanks!
Hi Sally, this batter as written is too much for just two 8 inch rounds, but you could try halving the recipe for two 8 inch rounds. Or, you could make the full recipe as written and divide among four 8 inch rounds for thinner layers. Hope your mom enjoys the cake!
Can whipping cream be substituted for sour cream? I’m not generally a fan of sour cream. . .or is it really best with sour cream?
Hi Tabitha, plain full-fat yogurt would be a fine substitute for the sour cream. This cake needs the thicker sour cream (or yogurt) for structure, whipping cream would be too thin.
Hi, I’m located in Aus and just wondering if natural cocoa powder is the same as cacao powder?
I looked at my local supermarket and all the cocoa powders seemed to be Dutch processed? Will they cake be okay if I just use that? Or should I use cacao powder. Thanks!
Hi Hayley! They’re not the same, we haven’t tested this recipe with cacao powder so we’re unsure of the results. Cacao can be more drying and bitter. This recipe needs acidic natural cocoa powder, so do not use all dutch-process cocoa powder. You can read more on the difference between the two in this blog post. If at all possible we recommend sticking with natural cocoa powder, sorry I can’t help more!
Hi Sally,
I was going to use this recipe to make cupcakes and then realized you have a full section within this recipe about cupcakes and list a completely different recipe to use instead of this one. Is there a reason for the recipe switch? Should I not use this recipe for cupcakes? Thank you!
Hi Rachel, you can use this recipe for cupcakes if you prefer, but it will have a much higher yield than the chocolate cupcakes. Let us know if you give it a try!
Hi Sally! Could I frost the outsise of my cake with mousse and omit the frosting? Thank you.
Some readers have done that and have reported back with great success!
Is this recipe adaptable to a bundt cake? Thank you.
Also, you are amazing! Your recipes have never EVER failed me.
Hi Diane, thank you for your kind note! We recommend using this Chocolate Bundt Cake recipe instead, and you can leave out the cream cheese swirl.
Thank you for the quick response. Will do
Hi Sally, Can i use this recipe for tier cake and use it as bottom tier..8 6 4 is my size. Thanks
Hi Rajal, we don’t have a chocolate cake recipe sturdy enough to be the bottom of a tiered cake at this time. It could work as a top tier, though! You can reference our cake pan sizes and conversions guide to adjust this recipe.
Absolutely delicious! I usually make cakes from a box because they usually turn out dry. I will definitely be making this again!
Hello! I love the look of this cake and can’t wait to make it, but it is cupcakes I’m after today. I did find your cupcake recipe and that looks great too, I am just curious why the sour cream is not included as it is in the large cake. Thank you!
Hi Abigail! Our super moist chocolate cupcakes recipe uses buttermilk instead of sour cream for a slightly lighter texture, this full sized cake needs the thicker sour cream for structure. You can try replacing the buttermilk with the same amount of sour cream in the cupcake reicpe if you prefer.
Hi Jean, the completed cupcakes should stay well in the refrigerator for up to five days, however, the closer you can assemble them to the wedding day, the better! See recipe notes for a few make ahead options, if you’re interested.
This is such an incredible cake. Its the kinda cake I get to spend all day making which is my favourite thing to do! Intensely rich and chocolatey. Thankyou for this recipe!
Hi
If I want to make a smaller cake I can use half of the measurement in this receipe ya?
Thanks
Hi Fatema, yes, you can halve the recipe for a smaller cake. (Our cake pan sizes and conversions guide might also be helpful to you for making smaller cakes).
Hi! Can this cake be made with six inch rounds?
I have successfully done this by halving the whole recipe
This cake is insanely good. Definitely a keeper! It is a bit labor intensive but my family said it’s the best cake that I have ever made!
The BEST chocolate cake recipe! So rich and decadent without being too sweet. Also very easy to follow along. Thank you so much for this gem of a recipe!!!!!
Hello! I have a question about this cake and it’s components. I baked the cake and made the mousse this last weekend in anticipation of my sons 2nd birthday dinner. Unfortunately he got sick and we’ve had to postpone the dinner until sometime next week. The cake can obviously be frozen, but what about the mousse?? We’re going to be leaving on a family vacation in a few days, so we won’t have time to eat it before we leave, but I also hate to let it go to waste and have to make more since it used ingredients that were on the pricier side. Would the mousse stay an OK texture if I froze and then thawed it next week?
Hi Anna! You can freeze mousse, but the texture is always a little different after thawing. It’s not quite as light and airy.
Can I make this cake with the filling a day ahead and store it in the refrigerator? Because I need to decorate on top and deliver it in the morning.. will it stay well for a day in the fridge?kindly help.. am making mousse filling for a cake for the 1st time and it’s for a customer.
I made and assembled the cake this evening, but won’t be serving it until tomorrow afternoon. Should I put the ganache on tonight or tomorrow?
Hi Liz, Either way works! If you have time to add it tomorrow you can. If you add the ganache the day before you can chill it uncovered for a few hours and then when the ganache it set you can cover the cake. If it hardens in the refrigerator overnight you will want to let it soften back up a bit before slicing and serving. Enjoy!
Hi Sally, can I use coconut oil instead of vegetable oil?
Hi Erin, you can try using melted coconut oil instead of canola but it will leave a slightly different taste.
I bake alot but have friends at church who are gluten free. Has anyone tried this with gluten free flour..I found King Arthur GF that measures equally to flour and have made many quick breads without issue but not an entire cake. Was wondering if there is anything different or tips someone might have for GF flour cakes thanks Love all your recipes Sally everything always turns out just wonderful
Hi Ginger, we haven’t tested this cake with gluten free flour, but let us know if you do!
This cake shows not hold together with gf flour