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.
Hey Sally!
This cake looks incredible – I was hoping there might be a way to modify the mousse to make a raspberry mousse? With white chocolate and dried berries maybe? I wasn’t sure how white chocolate would work though…
Hi Angela! I haven’t tried a white chocolate or raspberry mousse before and that would require some testing. I don’t want to steer you in the wrong direction, so I recommend finding another recipe for white chocolate raspberry ganache that has some good reviews!
Hi Sally! I’m looking forward to making this cake for my husband’s birthday! Any suggestions on making the chocolate mousse into a chocolate -hazelnut mousse? I was thinking of adding finely chopped hazelnuts directly into the mousse, but I would appreciate any other suggestions you have!
Hi RL! The best option– without risking ruining the mousse– would be to add finely chopped hazelnuts to it. You could also try stirring in a generous spoonful of Nutella, too. I also have a Nutella frosting that you could try on the cake instead of the ganache topping.
This was a huge hit at a church gathering! I gotta be honest, I was crazy busy and used a couple devils food cake mixes instead of mixing the cake from scratch, but followed the ganache and mousse recipes, and I assembled it exactly like the recipe. Everyone devoured it! Next time I’m not in a rush, I will make the cake from scratch also. This recipe is a keeper!
Sally, thank you for posting such foolproof recipes. This cake was amazing. Although somewhat in-depth it was totally worth 100% of our effort. My sisters and I made it for our younger sisters birthday. Huge success!!!
Thx
Hi Sally, This looks gorgeous, but I am wondering if I can use this filling for a chocolate swiss roll as the base of a Yule Log? Do you think it would stand up to that treatment? I’m making your chocolate cake for my son’s birthday next week. He loved it so much, he doesn’t even want me to make it for anyone else! Thanks Sally.
Hi Sora, this mousse filling would be great inside a Yule Log. As long as the log is chilled, the filling will be nice and sturdy inside.
Beautiful reciepe… I haven’t tried yet as a cake, but Imlove the all structures… I only upgrated a bit with salty caramel layer !!! Thank You!! For sharing!!!
When you are making the mousse, how do you keep the chocolate from seizing when you add the water? it mixes smooth but a bit grainy
Hi Hannah! Since the chocolate is already melted and the water is mixed with cocoa powder, there’s little risk that the chocolate will seize.
Hi Sally,
I am currently making this cake, in the recipe it says that the cake can chill up to 4 hours once the crumb coat is on. Do you think I can leave it at this stage overnight? Was thinking of just doing the ganache tomorrow morning for ease. Thank you!
Euge
Absolutely– you can apply the ganache the next day.
This recipe was amazing! It was super easy to make (although took a long time so be prepared to spend about 6 hours total on the cake). It tastes AMAZING. Like this cake could have been bought in a high class bakery. I highly recommend this recipe for the holidays, as it will feed many people and is delicious. I followed the recipe exactly and put raspberries on top and sprinkled powdered sugar just to make it look pretty. 10/10 would recommend
Ooh, I just love the layers of goodness. They look pretty and tasty! I wish GBBO dedicate full week to the dark chocolate baking
My cake was covered with your milk chocolate buttercream instead of the ganache since it was decorated for toddler’s bday but OMG that mousse is to die for. Everyone wants me to make their bday cakes now! Thank you Sally! We will definitely be making this mousse as a filling again and I already have made your buttercream, ganache and triple chocolate cake multiple times and always get raving feedback!
Tried this yesterday, absolutely delicious!
I used 3/4 100% natural cocoa powder and 1/4 dutch processed cocoa
I do feel like the cake that I baked seems to be on the flimsy side, and sticky on top. is that normal? should I have used more flour to have more firm consistency?
The reason I would like lit a bit more firm is to make it easier to work with while stacking it.
Thanks for the recipe!
Hi Jeannie! That’s a normal texture for this cake– it’s soft with deep flavor. You can try adding a little more flour to make it a bit sturdier if desired. Thank you so much!
Best cake ever!
I made this cake for my father’s birthday. The cake was superb. One of the best I’ve made.
I only had 2 nine inch pans so I made two cakes and cooked them until the toothpick came out clean ~30 minutes. I let the cakes cool completely before cutting them in half to make the four layers of cake. The cake was moist and delicious. I added 1 cup of dark chocolate chips to the cake batter instead of the semi-sweet chips. I brewed 1/2 cup of Ethiopian espresso coffee which I used as my liquid and I used 1/2 a cup of 1% milk with 1 Tbsp vinegar in place of the buttermilk.
The mousse filling was incredible. Light and delicious and I let the ganache drip down the sides like a drip cake. I saved some chocolate shavings for decoration.
Thank you for posting such an incredible recipe. Love, Love, Love!
I am hoping to make this next week for my bday, but instead of topping with ganache, I’d like to use your chocolate buttercream, and to pipe vanilla buttercream roses. Do you have any suggestions of things I should do differently, taking that approach?
Hi Samantha, You don’t need to make any other changes. It sounds like it will be a beautiful cake. Happy birthday to you!
This was amazing. I made it as described above, and I absolutely loved it. The mousse is amazing, and the perfect complement to the cake. Next time I may make it with the ganache, but as it was it was a little too chocolate-y for my husband (just meant more for me!).
I also ended up liking the frostings so much I’ve already used them again. I used the chocolate buttercream on brownies, and they disappeared in no time. The vanilla frosting was delicious, and so creamy.
Thank you so much for several great recipes
Hi Sally, can I make the ganache ahead off time like the day before?? Thanks, Vanessa.
Hi Vanessa! You can make the ganache ahead of time. Cover tightly and store ganache in the refrigerator for up to 5 days. Gently warm it to thin it out if needed.
I made this cake – which was sooo delicious and easy to make. The mousse was really good. I’m so glad you gave so much advice on using the different chocolates because it does make a difference. Now the ganache was good ( I used Guittard semi sweet wafers and some Ghiardelli semi sweet choco chips ) but it was on the thin side. My error may have been not chopping up fine or not enough chocolate. It tasted fine but I’ll be more careful the next time. Everyone raved about the cake and I must admit it had a delicious chocolate flavor . I wasn’t sure that I would like a dark chocolate cake but it was the best I ever tasted.
Hi Sally!
As I only have 2 cake pans, I was wondering whether I could divide the batter between the 2 and cut the baked cakes in order to create 4 layers. What do you think?
Thanks,
Claire
Thanks for the advice! I made the cake layers in 3 pans and it worked out fine!
Just a comment regarding the ganache – it turned out very thin and when I poured it on the cake it flowed everywhere on to the work surface, leaving only a thin layer on the cake itself…so I’m wondering if I should have chilled it in the fridge before use? I waited the 20 mins you suggest in the recipe. The cake was still delicious though!!!
Hi Claire! So glad it all worked out. Letting the ganache set for longer– or in the refrigerator– will allow it to thicken if it’s too thin after 20 minutes.
Thank you Sally for your prompt response . Will let u know how it turns out and will rate the cake . I can already predict it will be a5 stars…
Sonia
Hi Sally,
I am planning to make this cake for a party. I was wondering if you would recommend substituting cake flour for all or part of the all purpose? What effect would this have on the texture of the cake? Thank you for the recipe!
Hi Victoria! Cake flour isn’t strong or sturdy enough for this chocolate cake. Cocoa powder already lightens up the crumb enough, so you need all-purpose to help stabilize it.
Absolutely delicious! Dark, rich, decadent cake. I didn’t find the dark cocoa so used all regular and still so good with a deep chocolate flavor. Thanks for an amazing recipe!
❤️❤️❤️❤️❤️❤️ Love chocolate so much so this made my day! Will totally make again and again and again and again!!!! ❤️❤️
Hi Sally,
I’m worried about my mousse. When I combined the water/cocoa mixture with the melted chocolate, it became quite stodgy. Think of soft Play-Doh…not quite solid, but certainly not something I can “pour” into the whipped cream, as instructed to do.
If I try folding it into the mousse, I think it’ll be a massacre. Is there anything I can do?
Hi Jacquelyn, The chocolate mixture will be fairly thick but they will still fold together. You an see that mine isn’t a thin liquid in the photo above where I show the bowl of the whipped cream next to the bowl of the chocolate!
That time out of the refrigerator would be just fine, but for best taste, I recommend chilling in the refrigerator for at least 1 hour when you arrive and prior to serving.
Delicious! It was a huge success at the birthday party!
Looks intimidating but actually so easy to make 🙂
Hi Sally,
I made this cake for my daughter’s 25th birthday party. She loves chocolate so this cake was perfect. It was delicious, moist and not too sweet. I decorated it with white chocolate curls, raspberries and edible gold stars. It looked impressive and people asked where I bought the cake. Thank you for a super delicious recipe.
What a great recipe! A friend of mine asked me to bake a cake for her girls’ birthday party (she hates baking) and I tried this one out for the first time for the occasion (always a risk). I decorated it with dripping chocolate ganache and went over the top with decorations of chocolate waffles, melocakes, maltesers and chocolate sticks. It looked spectacular (if I say so myself) but it tasted just as good too! All the kids loved it and I scored big time My kids have requested the exact same cake for their upcoming birthday parties! So thank you so much for sharing this recipe!
Love this recipe, it is going in my family cookbook for sure. It is SO chocolatey and not excessively sweet. Each element is excellent- the cake is moist with deep flavour, the mousse is fluffy and rich and the ganache is a lovely finish. I will absolutely make this again.
What an amazing cake! I made this for my husband’s birthday and it was huge hit. The cake is moist and mega-chocolatey and the mousse is beautifully light. I will definitely be holding on to this recipe!
Hi sally! I’m making an assortment of 3-4 different types of cupcakes for my sisters birthday party and I’m trying to figure out which of your recipes to decide on..they all are incredible! But I LOVE this cake and I was wondering if the chocolate moose could be used to create a pipped frosting on top of the chocolate cupcakes? Thanks!!
Hi Lindsey, For cupcakes I usually fill the cupcakes with the mousse and then top them with a bit of the ganache. However, you can certainly just go ahead and pipe the mousse on top! It’s not sturdy enough for intricate piping but will still taste delicious!