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.

slice of dark chocolate mousse cake on a cake server

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 on a wooden cake stand

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 in glass bowl

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.

2 images of making chocolate mousse including whipped cream and chocolate mixture in glass bowls

Whipped cream + our chocolate mixture. ↑

Fold them together to make our chocolate mousse filling. ↓

chocolate mousse for chocolate cake in glass bowl and between cake layers

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!)

2 images of chocolate ganache in glass bowl and pouring 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 with berries and chocolate shavings

slice of chocolate mousse cake on a white plate

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

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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 (219g) all-purpose flour (spoon & 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

  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.
  6. 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.
  7. 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

 

833 Comments

  1. Literally the best chocolate cake!!! I have made multiple times and always turns out amazing. This time I didn’t have chocolate bars but I had a huge bag of Costco chocolate chips so everytime it called for chocolate bars I used chocolate chips and honestly it worked perfectly!! I always add the espresso powder and coffee when called for because it really brings out the chocolate flavor. Parchment paper on the bottom of the pan is a must!!! I’ve skipped this step before and ended up with chocolate crumbles! I buy parchment rounds on Amazon because it’s easier. I also usually pipe buttercream decorations for whatever the occasion is. Last night was my daughters 3rd bday so we did Minnie Mouse. The buttercream compliments the ganache and is not overpowering. This has become my go to cake. Follow the directions and make sure you have enough time to make it properly and it will be amazing.

  2. Is this cake strong enough to hold up to your Oreo icing from another recipe? Or would it be better to stick to the triple chocolate as a base?

    1. Trina @ Sally's Baking Addiction says:

      Hi Lauren, You can frost this cake with Oreo buttercream if desired!

  3. I love this recipe! I’ve used it so many times and it’s always a hit. I’m wondering if it’s possible to make this recipe as cupcakes! I’m having a party with a lot of little ones so I’m thinking it might be easier. Thanks!

    1. Stephanie @ Sally's Baking Addiction says:

      Hi Jen, It sure is! See the section of the post above called “What About Cupcakes?”

  4. Made this cake yesterday for a friend’s 60th birthday. Awesome cake. It was moist creamy dreamy all in one. Got a lot of compliments. Love love love it.

  5. Hi Sally!

    The cake looks delicious and I can’t wait to make it!

    Just wanted to know if can freeze this cake, and make a mirror glaze on top of frosting. I wanted to make a galaxy glaze for my son’s birthday!

    1. Lexi @ Sally's Baking Addiction says:

      Hi Athithya, we’ve actually never tried a mirror glaze before, but we can’t see why it wouldn’t work. Let us know what you try!

  6. Can I bake this In two 8 inch pans and cut them in half for the layers?

    1. Trina @ Sally's Baking Addiction says:

      Hi Maria! 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. Divide your batter, bake two layers, and whatever batter isn’t in the oven keep loosely covered at room temperature until your pans are ready to be used again. I hope you love the cake!

    2. Karin Gartside says:

      Hi Maria, I have also made this cake and I only put batter in two 8 inch pans. My tip is cook at 160c for about 30 mins check with skewer. When just clean take out of oven and leave in pan for 15-20 min. Place on cooling rack, when cool, wrap and freeze. I do a day or so ahead. Take out day you’re filling and when still frozen cut in half. Place back in fridge until filling it to keep cold. I do this method for all layered cakes. I hope this helps.
      Karin.

  7. Blimey Taub says:

    I don’t have Sour cream or Yogurt in the house…. Can I use more Buttermilk instead ? & would that B 1 ³/4 cup. Or less?
    Thanking you in advance!

    1. Trina @ Sally's Baking Addiction says:

      Hi Blimey, more buttermilk will be too wet for this cake batter, we recommend sticking with sour cream or yogurt if at all possible!

    2. Karin Gartside says:

      Hi Blimey, you would have cream for mousse and Ganache. If you have 3/4 cup extra , you could put a half teaspoon of lemon or vinegar to make sour cream. I hope this helps.
      Karin.

      1. Ohh ok. Thanks never heard of that substitute b4. I’ll have to give it a try.
        Thanku!

  8. Dianevictor says:

    Hi can I know what type of chocolate is preferred? Compound or normal chocolate works best? The one that melts easily and does not get harden fast.

    1. Lexi @ Sally's Baking Addiction says:

      Hi Diane, pure, quality baking chocolate bars work best here for the mousse and ganache. You can typically find them in the baking aisle. Hope this helps!

      1. Thank you so much for the reply appreciate it! Can’t wait to try this recipe out!

  9. Hi Sally, I have made this cake a couple of times and everything about is just perfect. I am going to make it again for my husband birthday and since he is a whiskey fan I am wondering if I can add some whiskey to the batter? What do you think?

    1. Lexi @ Sally's Baking Addiction says:

      Hi Shadi, we haven’t tried adding whiskey or another alcohol to the batter — it may take some experimenting to ensure you’re not adding too much additional liquid to the batter. Some readers have had success adding alcohol to their ganache, however — you can reduce the amount of cream by 1-2 Tablespoons, and use alcohol to replace it. Warm the cream on the stove as directed, pour over chocolate, then add the alcohol before you stir it all together. Let us know what you try!

  10. What we can use instead of egg please telll ????

    1. Lexi @ Sally's Baking Addiction says:

      Hi Soumya, we haven’t tested an egg-free version of this recipe, but do let us know if you give anything a try.

  11. I did the mousse recipe as a filling for chocolate cupcakes with chocolate ganache topping and sprinkles. They were absolutely delicious. Half a recipe would be enough for 24 cupcakes. Or do a full recipe and then use your leftover cake scraps and mousse to make parfaits.

  12. Literally it is the best ever chocolate cake recipe!!! I loved it❤️!

  13. Karin Gartside says:

    I’ve made this cake, myself recently. It’s just as delicious as it looks! So moist and very light with the mousse, also a great chocolate taste for those who love chocolate. I will be baking it again and again.
    Thanks for your recipe.
    Karin.

  14. Sharon Chelsea says:

    Can this recipe be halved ?

    1. Lexi @ Sally's Baking Addiction says:

      Hi Sharon, yes, you should be able to halve this recipe for two 8 inch or 9 inch round pans.

      1. Sharon Chelsea says:

        Thankyou so much ! Can’t wait to try it out .

  15. I skipped the parchment paper on the bottom as I was all out. I greased instead. DON’T DO THAT! I had to start over as the chocolate chips fused to my pan. But now I have delicious, delicious crumbles. The cake is delicious and the mousse and ganache worked perfectly. I wish I could post a photo. I’m so chuffed with how it turned out.

    1. Lexi @ Sally's Baking Addiction says:

      Hi Emma, we’re so glad this cake turned out well for you! If you’d like, feel free to send us a photo at [email protected] — we’d love to see it!

  16. Ginger Lemmons says:

    I bake alot but have friends at church who are gluten free. Has anyone tried this with gluten free flour..I found King Arthur GF that measures equally to flour and have made many quick breads without issue but not an entire cake. Was wondering if there is anything different or tips someone might have for GF flour cakes thanks Love all your recipes Sally everything always turns out just wonderful

    1. Lexi @ Sally's Baking Addiction says:

      Hi Ginger, we haven’t tested this cake with gluten free flour, but let us know if you do!

  17. Hi Sally, can I use coconut oil instead of vegetable oil?

    1. Hilari @ Sally's Baking Addiction says:

      Hi Erin, you can try using melted coconut oil instead of canola but it will leave a slightly different taste.

  18. I made and assembled the cake this evening, but won’t be serving it until tomorrow afternoon. Should I put the ganache on tonight or tomorrow?

    1. Stephanie @ Sally's Baking Addiction says:

      Hi Liz, Either way works! If you have time to add it tomorrow you can. If you add the ganache the day before you can chill it uncovered for a few hours and then when the ganache it set you can cover the cake. If it hardens in the refrigerator overnight you will want to let it soften back up a bit before slicing and serving. Enjoy!

  19. Divya Pravinkumar says:

    Can I make this cake with the filling a day ahead and store it in the refrigerator? Because I need to decorate on top and deliver it in the morning.. will it stay well for a day in the fridge?kindly help.. am making mousse filling for a cake for the 1st time and it’s for a customer.

  20. Hello! I have a question about this cake and it’s components. I baked the cake and made the mousse this last weekend in anticipation of my sons 2nd birthday dinner. Unfortunately he got sick and we’ve had to postpone the dinner until sometime next week. The cake can obviously be frozen, but what about the mousse?? We’re going to be leaving on a family vacation in a few days, so we won’t have time to eat it before we leave, but I also hate to let it go to waste and have to make more since it used ingredients that were on the pricier side. Would the mousse stay an OK texture if I froze and then thawed it next week?

    1. Trina @ Sally's Baking Addiction says:

      Hi Anna! You can freeze mousse, but the texture is always a little different after thawing. It’s not quite as light and airy.

  21. The BEST chocolate cake recipe! So rich and decadent without being too sweet. Also very easy to follow along. Thank you so much for this gem of a recipe!!!!!

  22. This cake is insanely good. Definitely a keeper! It is a bit labor intensive but my family said it’s the best cake that I have ever made!

  23. Hi! Can this cake be made with six inch rounds?

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