Dark Chocolate Mousse Cake

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.

dark chocolate mousse cake

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.

chocolate layer cake

3 Parts to Dark Chocolate Mousse Cake

Let’s break down each component of this intensely rich cake:

  1. 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.
  2. 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.
  3. 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!

4 layer chocolate cake

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!!

chocolate cake batter

Simplified Chocolate Mousse

The chocolate mousse adds a creamy and light contrast to the dark chocolate layers. You need 6 ingredients:

  1. Hot Water
  2. Cocoa Powdernatural or dutch-process
  3. Melted Chocolateuse two 4-ounce chocolate baking bars found in the baking aisle
  4. Heavy Cream
  5. Confectioners’ Sugar
  6. 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.

making chocolate mousse

Whipped cream + our chocolate mixture. ↑

Fold them together to make our chocolate mousse filling. ↓

chocolate mousse for chocolate cake

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 on chocolate cake

Chocolate Ganache

I won’t go into a lot of detail about the chocolate ganache because I have a complete chocolate ganache recipe 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. 🙂

top of chocolate mousse cake

chocolate mousse cake

What About Cupcakes?

Instead of a big cake, you can make chocolate mousse cupcakes. Use my chocolate cupcakes recipe and halve the chocolate mousse and chocolate ganache recipes below. Fill the cupcakes with chocolate mousse using my Sugar Plum Fairy Cupcakes as an example. Drizzle cooled cupcakes with ganache. Eat your heart out!

More Indulgent Chocolate Desserts

Print
4 layer chocolate cake

Dark Chocolate Mousse Cake

  • Author: Sally
  • Prep Time: 2 hours, 30 minutes
  • Cook Time: 25 minutes
  • Total Time: 5 hours, 55 minutes
  • Yield: serves 10-12
  • 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 (220g) all-purpose flour (spoon & leveled)
  • 3/4 cup (65g) 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

  1. Preheat oven to 350°F (177°C). Grease four 8-inch or 9-inch cake pans, line with parchment paper, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans.
  2. 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.
  3. 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.
  4. Remove the cakes from the oven and set on a wire rack. Allow to cool completely in the pan.
  5. 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.
  6. Assemble layers before preparing chocolate ganache: First, level the cakes if needed: using a large serrated knife, slice a thin layer off the tops of the cakes to create a flat surface. Discard (or crumble over ice cream!). Place 1 cake layer on your cake stand or serving plate. Using a large icing spatula, evenly cover the top with about 1.5 cups chocolate mousse. Top with 2nd layer and evenly cover the top with 1.5 cups chocolate mousse. Top with the third cake layer, then spread another 1.5 cups mousse evenly on top. Save a large spoonful of mousse for a thin crumb coat. Top with final 4th cake layer. Spread any remaining mousse around the sides as a crumb coat. Run a bench scraper around the cake to smooth out crumb coat. Refrigerate cake for at least 1 hour and up to 4 hours. Prepare the ganache as you wait.
  7. 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.
  8. 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.
  9. Cover leftover cake tightly and store in the refrigerator for 5 days.

Notes

  1. 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.
  2. 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 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.
  3. 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.
  4. 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.)
  5. Why Room Temperature? All refrigerated items should be at room temperature so the batter mixes together easily and evenly. Read here for more information. Instead of sour cream, you can use plain yogurt. The cake won’t taste as rich, but it’s a fine substitute. If needed, you can use whole milk mixed with 1/2 teaspoon of white vinegar or fresh lemon juice instead of buttermilk.
  6. Chocolate in Mousse & Ganache: Mousse & ganache will only set if the correct chocolate is used. You can use high quality chocolate chips if needed (I prefer Ghirardelli semi-sweet chocolate chips), but I recommend using pure chocolate baking bars. You can find them right next to the chocolate chips in the baking aisle. They are sold in 4 ounce bars. I like Bakers or Ghirardelli brands.

Keywords: cake, chocolate mousse, dark chocolate

 

129 Comments

  1. My jaw just dropped open and stayed that way when I saw this recipe five minutes ago. Am I dreaming?! Because this cake is like…life. It’s gorgeous. And I’m 100% positive that it is deeeeeelicious as well! All the mousse! And ganache! And DARK CHOCOLATE CAKE (!!!). And here I was wondering what to bake next…obviously that kind of thought will never cross my mind again, because…hello…this cake. So, thanks for perfecting my existence, Sally 😀

  2. Oh, and happy birthday to Kevin! He is so lucky to have gotten this as his birthday cake. Who even needs presents if they recieve a cake like this?! I say just give me a fork and leave me alone for a few hours…minutes…seconds.

  3. Hi Sally
    Love all your recipes!!! I don’t you any other site now!
    U thee best!!!
    Would this recipe still turn out if I cut the sugar down
    1 1/4 cup sugar

  4. Hershey’s recently changed the formula of their Special Dark cocoa to be 100% dutched cocoa instead of the blend that it used to be. Just a heads up since the change can throw off the leavening in recipes made for a blend with natural cocoa.

  5. Oh Sally, I really want to make this cake…….like now. I’m totally salivating. But there’s one small problem- my daughter is on a red eye and I have to get her in two hours! That, and I spent the day baking your honey oatmeal bread, cheese crackers, and brownies. However, I simply must make this before she goes back to Denver, but I’m going to halve the recipe. As much as we’re chocoholics, (like mother, like daughter!), I don’t think we’ll be able to power through a whole cake, even with her teenage brother’s help! Me thinks after making this, she just might want to move back home, LOL! I’ll report back how it turns out!
    P.S. I cut the cheese crackers in animal shapes…turtles, ducks, and they are really cute! The leftover dough stayed in the fridge for 5 days and tasted just as good as the batch I baked on day one. They are highly addictive and my boys loved them!

    1. I hope you have a great visit with your daughter!! What a delicious dessert to make for your family 🙂 Your cheese crackers in animal shapes sound absolutely adorable!! Such a fun idea! Happy baking!

      1. Hi Sally! I can’t wait to make this dessert this weekend! What about baking the 2 pans, then using a long serrated knife to split them in half, making 4 layers? About how much baking time would the 2 pans require? Thank you!

      2. That could definitely work. I recommend two 9-inch cake pans. The bake time will be close to or over 25-26 minutes– keep your eye on them and use a toothpick to test for doneness.

  6. Hey Sally! I simply couldn’t resist making this right away…..the combo of cake, mousse and ganache is ultimate indulgence!! Unfortunately, my chocolate cakes sank in the middle…..any tips/advice to avoid this next time? The mousse turned out perfect! Waiting for the cakes to cool now. Thanks, Nona

    1. Hi Nona! Over-filling the cake pans or under-baking the cakes will result in sinking in the center. Were they baked all the way through? Love this mousse!

  7. Sally,
    You literally read my mind. After the cheesecake challenge and recently making your chocolate zucchini cake this cake concept came to life. I had chocolate mousse, chocolate ganache and a dark chocolate cake with chocolate chips as my new inspiration to bake. So to see you make it first makes me beyond happy. This will be my go to cake because it combines all my favorite things abut a chocolate cake. I will make 6″ cakes with this recipe and complete the recipe. Plus, my dad and I can share this chocolate cake as a joint birthday cake. It will be unforgettable.

  8. Your chocolate cakes and cupcakes are divine. Several cakes have given relatives that I am one hell of a baker. I say, don’t give me any credit, it’s that Maryland girl.

    I can only imagine this cake will be even better. Is that is even possible? Thank you so much.

  9. What kind of Buttermilk do you all use? I’m not really much of a baker and every time a recipe calls for buttermilk, I never know if I should buy can or the Cultured Buttermilk where the regular milk is. I tried doing the Whole Milk/vinegar before, but I don’t think that it turned out right. Any suggestions on what kind to get? Thanks

    1. Cultured buttermilk is actually what you want – it’s how it’s sold in stores in the U.S. I have heard from many other bakers that they use the powdered buttermilk sold in the baking aisle that you mix with water and they all say that works well also!

  10. Sally that cakes looks INCREDIBLE! Can’t wait to try it! Just a question, I can only get the Hershey’s Natural Cocoa Powder, the Dark Dutch Process doesn’t exist where I live. If I go to a special baking store, what kind of substitute should I used? I mean, in terms of the porcentage of cacao so I can buy the powder and make the blend you mentioned.

    1. Hi Laura! Just use ALL natural cocoa powder. The cake will still be plenty dark, especially with the addition of espresso powder and hot coffee (instead of water).

      1. Thanks Sally! I don’t know why I didn’t get your answer until now! But I have this cake on my bucket list! Thank you again! Big hug!

  11. Hi Sally, this dark chocolate cake looks gorgeous. I’m not a baker, but love to bake once in a while. My question is regarding chocolate mouse. Do you have to wait for the melted chocolate to cool completely before mixing is with the whip cream?

  12. Can’t Wait to make this cake, I will make it for our next spaghetti supper at Church. I will try to remember to take a photo.

  13. Hi Sally.
    What brand of chocolate do you recommend for the semi-sweet chocolate bars for the ganache? I am having a large crowd for a cookout this weekend and 5 birthdays to celebrate, and this cake looks like the perfect choice!

    1. Hi Danielle! I recommend using my chocolate cupcakes recipe as the batter to make a 3 layer 6 inch cake. See my 6 inch cake recipes as a guide. Halve the chocolate mousse and ganache so there’s just enough.

      1. Hi Sally, if I use that cupcake recipe should I still replace the buttermilk for sour cream? Thanks!

  14. Hi Sally,

    I am a huge fan of yours. This cake looks heavenly!! I am wondering if it would be too much to add raspberry sauce inside the cake. I love chocolate and raspberry combo.

    Thanks,

    Sam

  15. Is the video posted to YouTube? How about a “Jump to” link that I saw on another blog since you do so many videos now? I just don’t always see them show up on my iPad.

    1. Hi Cheryl! There’s a Jump To Recipe feature, but not a Jump To Video feature– the Heading should help you find the video a little faster though! The video is on YouTube and my Facebook page, yes!

  16. I would love to make this but can you add a layer of jam or cherries ( similar to a Black Forest cake) between the cake with mousse?

    1. I can’t see why not! It will be imperative to chill the cake in the refrigerator before serving and frosting with the ganache to ensure that the cake holds its shape.

  17. Sally this is the most beautiful beautiful breath-taking cake you have ever showed us! Guranteed am making within a few days. Thank you

  18. Oooooh Sally , you did it now !! I’m baking this cake and I know how. The secret is out you posted it here . My husband is begging for it, oh dear. You do it to us all the time it’s so true. Just keep them coming Sally I’ll be baking those too!!!
    You & your team are awesome love it .

    1. Hi Greta, The last paragraph of the post (just above the recipe) says “What about cupcakes?” The directions are there for you! 🙂

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