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’m so excited to make this! Would this recipe work well halved (so, to make 2 layers instead of 4) or would you recommend using the full amount but baking them as two cakes instead?
Hi Zoe, 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 Sally! Do you even off the tops of the cakes before assembling?
Hi Alexandra! Yes, if they are domed, we will level the cakes before assembling.
I made this for my son’s birthday and everyone went crazy over it .. I added some brandy extract to the mousse and plan on adding cooking rum to the cake next … it is soooo moist and creamy and chocolatey … best cake ever !! Ever !!!
I’d like to make this cake but with a white chocolate mousse filling, would I do the same method as the chocolate mousse but omit the cocoa powder?
Hi Amanda, we’ve actually never made white chocolate mousse before, so we’d recommend finding a white chocolate mousse recipe you love and using that as the filling. Or you might be interested in this tuxedo cake where we use white chocolate ganache between the layers. We’d love to know what you try!
Hi! Everywhere around me is sold out of baking bars. I ended up having to buy ghirardelli semi sweet choc. chips. How do I substitute those in the recipe instead of the baking bar?
Hi Amanda, we really recommend baking chocolate bars for best results, but those high-quality chocolate chips should work when the bars aren’t available. Same amount. Enjoy!
Can you bake this in a 9 x13 inch pan?
Hi Susan, You can bake this cake in a 9×13 inch baking pan. Same oven temperature, about 35-40 minutes bake time.
Hi Sally! thank you for an incredible recipe! im gonna have a birthday order and tried this recipe for a trial and it tasted amazing. altho i have a few questions, my mousse is a little bit liquidy and thin, i tried not to overmix it, i just fold it so that its equally combined and i whipped it until medium peak, should i do it until hard peal instead? and since i made it for a trial, i only use halve of measurement on loaf mould, and cut it as layer, and as i cut it, it crumbles, is it supposed to crumble or was it too dry? (i realized my sour cream only has 10% fat). and last question, is it possible to bake the cake a day before without freezing it?, and assemble them the next day, bcs my oven is too small for 2 pan at the same time, so it would take a day to make 4 layers and let them cool one by one.
im really sorry for the long questions, but i really thank you in advance for your response. and i also thank you again for the recipe, its so well explained and so detailed.
have a nice day!
Hi Shasa, The most common cause of a thin mousse is over mixing. If you try it again, avoid over-mixing which can deflate/thin out the mousse. And also, make sure you chill it in the refrigerator for at least 2 hours before using. This cake is very moist so it’s not surprising that it crumbled when you tried to slice your layer in half. When you bake separate layers in a pan and don’t split them, you shouldn’t have this problem. If you bake your cake layers you can cover them tightly and store them at room temperature for one day. Hope this helps!
If I could leave a 10 star rating for this cake then I would!
Made this gorgeous cake for my birthday yesterday and it came out absolutely perfect! My entire family said it was one of the best cakes that they have ever had.
Easy straightforward recipe.
Thank you for sharing this wonder of a cake !
I truly make this cake at least 4 times a year for birthdays/special occasions, been making it for years now. Everyone always asks for it. Make sure to have fresh raspberries to go along with it. It makes the cake that much better. Everything about the cake is perfect and such a good recipe!
Whatever you do, don’t add the chocolate chips. The hard crunch completely ruins the cake.
Hi Sally,
I’m looking to make a cube/square shaped cake with 8″ square pans. I was thinking of using two whole batches (so 4 8″ square cakes total) to get the proper height. Do you think it’s okay to use one batch between 2 pans?
Thanks,
Erica
Hi Erica, It’s too much batter to only use 2 pans. Overfilling your pan will cause the cake to bake unevenly and because there would be so much batter it would be too heavy to rise properly. You could make it as a 3 layer cake instead of 4, see recipes notes for details.
I added chocolate chips (full size) to the cake batter and really wish I hadn’t. I served the cake semi-chilled and biting into a soft cake and hitting a chunk of solid, non-melty chocolate was not a pleasant experience. Sadly, it kind of ruined the cake for me. Maybe mini chips are okay. Otherwise, cake texture was good. A little less sweet than I prefer my cakes. The mousse was okay, although, again, not quite sweet enough to taste decadent.
Looks delicious..I am sure I am gonna try. Can you please suggest what can I substitute for eggs
Hi Sally! The cake is chilling in the fridge tonight, will finish tomorrow. Instead of a spreadable ganache do you think I could do a thinner version to drip? And if so do you have a recommended recipe? The cake and mousse taste a-mazing!
Hi Michelle! Allowing the ganache to cool for less time before using should result in a good drip consistency. Let us know if you try it!
Oops, I posted my comment as a reply to someone else’s rather than as a new comment. Apologies. My question was, do you think this could this be made using white chocolate?
Hi Karen, we’ve actually never made white chocolate mousse before, so we’d recommend finding a white chocolate mousse recipe you love and using that as the filling. Or you might be interested in this tuxedo cake where we use white chocolate ganache between the layers. We’d love to know what you try!
I have Lindt & Ghirardelli dark chocolate bars, both are 3.5 Net Wt Ok yo use either ??
Hi Dottie, you can use these combined for 7 ounces of chocolate. I would reduce the heavy cream to 7 ounces. (You want equal parts cream and chocolate for the ganache.)
Hi Sally! I ve made several times this cake and every time it’ is a hit!!
My niece asked me for colored blue cake smurf theme and I was wondering if Italian buttercream would be OK to cover the outside instead of ganache. I Don t like American buttercream. Do you have any other proposal?TIA
Anna
Hi Anna! Italian buttercream would be wonderful, or you may enjoy our Swiss meringue buttercream recipe as well. Happy baking!
I have made this several times and everyone loves it! Thank you very much for the recipes..❤️
My chocolate mousse liquify when folding the whipped cream (it was fluffy firm) with the fudge mixture (melted chocolate&cocoa) 🙁 help How to make it firm again ?
Hi Veronica, The most common cause of a thin mousse is over mixing. If you try it again, avoid over-mixing which can deflate/thin out the mousse. And also, make sure you chill it in the refrigerator for at least 2 hours before using.
So I’m planning on making this recipe into cupcakes for a good friend’s birthday (I’ve made it in layer cake format before and it was amazing, so I’m back for cupcakes!), and I was wondering, if I wanted to fold some chopped strawberries into the mousse to fill the cupcakes, do you think that would work? Or would the water content of the strawberries make the mousse too wet?
Thank you so much in advance!
Hi Ceilidh, for best taste/texture/presentation, we recommend only using berries on top. The mousse may liquefy a bit with sliced strawberries inside.
Okay, thank you so much!
I want to make a mirror glaze – do you think that would work instead of the ganache with this cake?
I don’t see why not!
Hello! I want to make this cake for my sons birthday but he wants chocolate cake with white frosting – which frosting recipe do you think would go the best with this cake?!
Hi Shanna! This cake would be delicious with vanilla frosting 🙂
Hi! I followed the recipe to a T. Everything turned out how it should have except I found the actual cake batter turned out drier than I was expecting. I was hoping it would be moist. Where did I go wrong? I used buttermilk, sour cream, hot coffee even read the extra directions and only baked the cakes at 19 mins to ensure they would be moist!
Hi Meg, Usually if a cake is dry, it is either overbaked or there’s too much flour. How did you measure your flour? Be sure to use the spoon-and-level method. `
Can I use unsweetened Baker’s Chocolate if that’s all I have?
Hi Maria, no I do not recommend unsweetened chocolate. With regards to the other comment about receiving no response– my team did not know the answer to your question so it was left for me.
My apologies for being impatient. You have amazing recipes.
Does this cake rise a lot? I’m making a 6 inch version and wondering if I have to fill the pans 1/2 or 3/4 full.
Hi Nancy! We recommend filling 1/2 way full for light and airy chocolate cakes like this one.
I just have 2 8 inch pan, can i separate in 2 pans and cut the cake after? Or should i bake 2 cake, remove them from the pan and bake the other one after?
Hi Cynthia! The best way would be the second option you described – the cake batter can sit at room temperature until the pans are free to use again. Enjoy!
I did that and they turned awesome. Thanks. Can’t wait to put everything together and serve it tomorrow
Hi there.
We LOVE this cake. Love it. The cake is ridiculously moist and delicious.
My daughter wants a chocolate cake for her birthday (she’s 5), but wants it decorated with a Wonder Woman theme. I was wondering how you thought this cake would handle vanilla buttercream in between the layers (instead of the mousse) and as the frosting so that it could be dyed and decorated?
Thank you in advance.
Hi Kelly! Yes, you can use vanilla buttercream with this cake instead of the mousse. You may also love our triple chocolate cake recipe. Hope it’s a hit!
Would you recommend using cake flour for this recipe?
Hi Missy, we don’t recommend using cake flour in this recipe. Chocolate cakes already have cocoa powder— which is a VERY fine dry ingredient. The combination of cake flour and cocoa powder usually results in a flimsy cake.
Hersheys Special Dark Cocoa is definitely the secret. I’ve done with Fry’s Cocoa but there simply is a huge difference in flavour. Kids said it was the best.
I’ve been eyeing this cake for so long and finally made it. Wow, I thought I would miss some type of buttercream, but the mousse makes you forget about frosting all together. I used espresso powder and coffee and the cake alone is amazing, but with the mousse and ganache, it’s top 3 best cakes I’ve ever made and I’ve made a bunch. Thanks for this great recipe!
Hi! Can I sub the buttermilk with something else?
Hi Myrka, Buttermilk is required for this recipe. You can make your own DIY version of buttermilk if needed – see recipe notes for details.
Hi Sally! Before adding the hot coffee, should we mix the dry ingredients and buttermilk mixture to avoid cooking the eggs?
Hi Skye, Yes, The hot coffee will be the last ingredient you add after the buttermilk (but before the chocolate chips if you are using). See recipe step 2 for the correct order of mixing the ingredients.