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.
Can I substitute almond flour for the all purpose flour?
We don’t recommend almond flour as it has very different baking properties and is not usually a 1:1 swap. We haven’t tested it, but you might have success experimenting with a gluten-free all-purpose flour like Bob’s Red Mill or Cup4Cup. If you give anything a try, we’d love to know how it goes for you!
Thank you! It’s for my daughter’s 21st birthday Saturday and she is gluten intolerant
Hello from one Sally to another! I’ve seen your recipe for chocolate cupcakes but was wondering if I could use this dark chocolate cake recipe to make cupcakes also? Thank you!!
Hi Sally! You can certainly use this recipe for cupcakes — it will yield about 3 dozen. You can follow the bake time instructions from chocolate cupcakes as a guide.
Hello, could I use the mousse as a topping for brownies or a single layer sheet cake, or does it need to be used as a filling?
Hi Christine! You can definitely use the mousse as a topping.
Would the mousse make a good topping for brownies? Or does it need to have something covering it to not dry out?
Hi Christine, we haven’t tried it, so can’t say for sure, but it would probably be delicious. You’d just need to keep it covered and in the refrigerator and serve the brownies cold. You could also try doing a layer of chocolate ganache over the top of the mousse–so decadent!
Hi Sally,
I was reviewing your chocolate mousse recipe and it looks so good! Also, your reviews are so
I really want to prepare your mousse reception as fillings between four chocolate cake layers and the cake will be frosted with chocolate buttercream frosting. However, I am baking this cake for a school auction. I am wondering if the cake will still taste ok after sitting out on a table for a few hours. This event will probable last from 5:00pm until late night.
Any suggesions would be highly appreciated.
N
Hi Darryl, the cake will be fine at room temperature for a few hours. If you can refrigerate it beforehand, that would be great.
Thank you so much Sally! I just have two more questions that I should have asked earlier.
Would refrigerating a cake, wrapped in Saran Wrap dry the cake out or keep her moist once out at room temp.
Would it be ok to add an orange zest to the mousse? I just think it the hint of orange would add to the chocolate.
Thank you.
Hi Darryl, covering the cake in Saran wrap will not dry the cake out. A cake box or cake carrier are also great options for storing in the refrigerator. You could definitely add a bit of orange zest (to your taste) to the mousse. Enjoy!
Thank you Sally.
Can I use decaf coffee instead of regular coffee for the taste without the caffeine?
Hi Kim, that shouldn’t be a problem.
WOW! I have been baking for over 20 years, I have a tried and true chocolate cake recipe that my family loves. I make this cake for my Mother’s 76th Birthday and it was The Best Cake I’ve ever made! I made it in steps, it was easy to put together and everyone loved it! It will be in my rotation now for any occasion. Thank you Sally!
So happy to read this, Michelle!
If I plan to make this cake as a 9×13, should I divide the mousse in half? I’m afraid it will be a lot for just one layer.
Hi Heather, you can definitely halve the mousse portion for a 9×13 cake. Enjoy!
Can I use butter instead of canola or vegetable oil in the cake batter?
Hi Kimberly, We recommend sticking with oil in this cake– it’s the power ingredient providing a lot of moisture to the baked cake. You can try replacing with melted butter, but the cake will taste different and may not be as moist. You can also try melted coconut oil instead of canola (again it will leave a slightly different taste).
Thank you! What types of vegetable oil do you recommend? Avacado oil? Olive oil? Sunflower oil?
Hi Kimberly, we recommend regular vegetable oil or canola oil for the most neutral taste. The others you mention will change the flavor of the cake a bit.
I made this yesterday and everyone said it was the best chocolate cake that they had ever had! Surprisingly very light…absolutely delicious!
Can Black Cocoa be used as a substitute anywhere in the recipe?
Hi Rose, Black cocoa powder is a dutch process cocoa powder. This cake recipe needs acidic natural cocoa powder, so do not use ALL dutch-process cocoa powder. You can use a mix of both – see recipe notes for details.
Hi! If I assemble the cake ahead of time and put in refrigerator before the ganache step, do I need to cover/wrap the cake?
Hi Jessica, you won’t need to wrap the cake if it’s just refrigerating for the 1-4 hours in step 6. If you are preparing the cake the day before and plan to refrigerate overnight, we would recommending covering the cake.
I made this for my mom’s birthday because she is a huge chocolate lover and especially loves chocolate mousse. The recipe had an egg free mousse and was not too complicated so that’s what grabbed my attention. I made the cake into 3 layers and had a bit of leftover ganache (which I rolled into truffles). My mom ADORED this cake and couldn’t get enough of it. I personally think it is one of the best cakes I have made and it was so easy to do!
Where did you purchase the wood cake plate?
Hi Gerry, it’s from Pier 1 from a few years ago.
Hi! Would it be possible to divide in two 9×13 rectangular pans?
Hi Sarah, You can use this full amount of cake batter (not doubled) to make a 9×13 inch cake. Bake for about 40 minutes in a 9×13 inch cake pan. Same oven temperature.
Hi Sally, I tried to read through some of the comments to find an answer, but I’m on a time crunch and don’t have time to sift through ALL the comments. I just need to know if using 4 pans is necessary? If I use 2 -9” pans can I just torte the cake(s)? If so, how long should I bake the cakes?
Hi Lydia! You can divide this batter between three pans (see recipe notes), but there is simply too much batter to bake properly in only two pans.
Can I use dark chocolate for the mousse?
A bittersweet chocolate would be great. Semi-sweet is considered “dark” but bittersweet is typically darker.
This recipe is delicious! However, I had a mishap and dumped my fourth layer in the oven by accident! So, I made another recipe of cake mix to have the fourth layer. My question: Can the cake batter be refrigerated or frozen to use at a later date?
Hi Dossie! Cake batter should not be frozen. The cake layers can be baked and frozen, though. See Make Ahead & Freezing Instructions in the recipe notes for details.
Hi sally. I love this but I find my cake sinks in the middle. Would you have any tips for that? Thanks.
Hi Linda, a little sinking in the middle is normal for chocolate cakes, but it can also mean that the cake is slightly under baked. An additional minute or two in the oven will help. Be sure that your baking powder and baking soda are fresh, too. We find they can start to lose their power after about three months, even if they’re not expired. Hope these tips help for next time!
This recipe was so much loved by everyone who ever tasted my cake! Thankyou Sally for this wonderful recipe
could you make this in a 9×13 pan and put the Mousse on top of it and the ganache on top
Hi Doris, you can use cake batter to make a 9×13 inch cake. Bake for about 40 minutes in a 9×13 inch cake pan. Same oven temperature.
hi! is there any substitute for sour cream?
Hi Rae Anne, full fat plain yogurt is a great substitute for sour cream in this cake.
For years, I have been searching the perfect chocolate cake recipe and I found it! Thank you! I made this cake for my mother’s 90th birthday (I doubled the recipe which worked out well), and it was amazing! I can’t wait to make it again! Thank you so much!
Will freezing an unfrosted mousse-filled cake affect the texture of the mousse? Thank you!
Hi Dee, You can freeze mousse, but the texture is always a little different after thawing. It’s not quite as light and airy. We’d recommend freezing the individual cake layers and then making the mousse fresh when you’re ready to assemble.
Hi! Could buttermilk be substituted with 5% sour cream? Thank you!
Hi Dee, Buttermilk is required for this recipe. You can make your own DIY version of buttermilk if needed – see recipe notes for details.
Hi Sally, first of all love your recipes! I have made this cake a couple of times and it always turns out great! However, this time I experienced an issue with the chocolate mousse – when I incorporated the chocolate mixture into the whipped cream, the chocolate turned into lumps rather than smoothly mixed into the mousse. Could it be that it cooled down a bit too much? I only left it on the side for 5-10 minutes as I was whipping up the cream. Fingers crossed it still turns out great!
Hi Christine, I wonder if yours cooled too long, and solidified. It should really only be set aside for a few minutes as you whip the cream. So, it will still be a bit warm when you fold into the whipped cream mixture.
I always use a whipped ganache as the fluffy frosting between cake layers. Just make ganache with the chocolate and heavy cream. Let it cool. Then whip. Works perfectly!!!
Hi Sally! I’m in the middle of this recipe. I’m wondering if I can leave the cakes out over night and assemble it all in the morning. I’m gonna try it. Maybe I should cover them and they’ll be fine? (they are totally cooled by now and still in their pans)
Hi Celina, we recommend removing the cakes from the pans and covering them in plastic wrap to help seal in the freshness (so they don’t dry out overnight). You can leave the wrapped cakes at room temperature overnight.
Hi Sally, I absolutely LOVE this recipe. I have baked it multiple times.
But I have to bake it in 7” pans(on someone’s request)
I know you have suggested your cupcake recipe for smaller pans… but I really want to bake this one.
Will it not work if I fill the pans only 2/3 ?
And use the rest of the batter for cupcakes.
Or
Any other suggestions ? I don’t mind having more batter and using the rest in other pans
Pls let me know.
Thanks 🙂
Hi Rakhee, that will work just fine as you mention!
Hi Sally, have you tried this recipe with sea salt sprinkles? Would love to try it for an upcoming event! Thank you!
Hi Misty, we haven’t, but let us know if you do!
I’m excited to taste the cake. I made 2 9” inches can I refrigerate them and cut in half? TIA
Could you add the raspberry layer from your chocolate raspberry cake to this one or would the mousse not support it???
Hi Dianna, we haven’t tested it yet, but you should be able to add the raspberry filling to this cake. If you try it, please let us know how it turns out!