Everything you could ever want in a chocolate cake is right here in this dark chocolate mousse cake! It consists of four layers of incredibly moist chocolate sponge, decadent dark chocolate mousse, and silky dark chocolate ganache. It’s a chocolate on chocolate dessert yet it isn’t overwhelmingly rich, it’s just the right amount of decadence to satisfy that chocolate craving.
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Why you'll love this dark chocolate mousse cake
- Rich, Decadent Flavor: The combination of moist cake, creamy mousse, and fudgy ganache makes this dessert feel extra special.
- Fudgy, Moist Texture: Unlike most chocolate cake recipes, this recipe bakes up incredibly fudgy & moist with a pronounced chocolate flavor and a melt-in-your-mouth texture that is utterly irresistible.
- Simple, yet Impressive: This cake requires zero decoration and instead relies on the beautiful layers to impress! It's also the perfect dessert to bring to a party, since the assembly in the pullman pan makes it so easy for transport.
For more chocolate cake recipes, try my Ultimate Chocolate Fudge Cake, Chocolate Swiss Roll, Chocolate Tiramisu Cake, and Mini Flourless Chocolate Cake.
Ingredient Notes
- Flour: Use high-quality unbleached all-purpose flour.
- Cocoa Powders: Use a combination of dutch process and black cocoa powders for an extra rich flavor. Alternatively, you can use unsweetened cocoa powder, but it will not be quite as rich.
- Leavener: Baking powder is all you need to give this cake the perfect rise and texture.
- Oil: Use a neutral oil such as light-tasting extra virgin olive oil.
- Coffee: Add freshly brewed hot coffee at the end to "bloom" the cocoa powders in the cake.
- Chocolate: Use your favorite dark chocolate chips, chunks, or bars!
See recipe card for full information on ingredients and individual quantities.
Step by Step Ingredients
Here are step by step photos and instructions on how to make this chocolate mousse cake! For the full ingredient list and method, see the recipe card at the end of this post.
Bake the cake
In a medium bowl, whisk together the flour, sugar, cocoa powders, baking powder, and salt. In a large bowl, whisk together the milk, oil, eggs, and vanilla. Add the dry ingredients to the wet and whisk until just combined. Lastly, whisk in the hot coffee. Pour the cake batter into the prepared pan and wrap the soaked cake strips around the outside of the pan. Bake for about 25 minutes.
Make the dark chocolate mousse
In a small saucepan, bring 170g (¾ cup) heavy cream to a simmer, then pour over the chocolate and mix until smooth. Whisk in the egg, vanilla, and salt. In a separate small bowl, whip the remaining 113g (½ cup) heavy cream to stiff peaks. Fold the whipped cream into the chocolate mixture. Pour into a shallow dish and press plastic wrap up against the surface and chill for at least one hour.
Make the dark chocolate ganache
In a small saucepan, bring the heavy cream to a simmer (or about 190 degrees F), then remove from heat, add the chocolate, and mix until smooth.
Assemble, chill, then serve
Cut the cooled cake in half, and each half into two layers, giving 4 layers measuring roughly 9x5. Add the first cake layer to the bottom of the pan and top with ⅓ of the mousse. Repeat with the remaining cake layers and mousse. Pour the warm ganache over the assembled cake and spread into an even layer. Place the cake in the fridge uncovered and chill for at least two hours before serving.
Expert Baking Tips
- Use a cake strip to create a flat cake. Soak these wilton cake strips in ice water before starting the cake batter. Just before baking, wrap the cake strips around the pan. The cold temperature on the outside of the cake will prevent the edges from baking faster than the center, resulting in an evenly baked flat cake.
- Use a cookie scoop to portion the filing. To add an even amount of filling to each layer, use a cookie scoop. I used a 3 tablespoon scoop and added 4 scoops to each layer.
- Chill the cake for at least two hours. To ensure the mousse and ganache have thickened up and the cake cuts easily, chill it uncovered for at least two hours!
Recipe FAQs
Dutch process cocoa powder is THE best cocoa powder for baking. Because it's neutralized with an alkalizing agent, it has a smoother flavor and creates the most fudgy and chocolatey baked goods! Black cocoa powder is similar to dutch process, but richer in flavor and darker in color. It is typically used in small amounts alongside another cocoa powder to enhance the color and flavor of the baked good. It smells like actual chocolate cake and is just magical to bake with! I always buy this King Arthur black cocoa powder.
Cakes may dome in the middle when they bake because the outside bakes faster than the center, so the center has more time to rise. This is not ideal for layer cakes, because it is a pain to have to trim away the top of the cake. The best way to ensure your cake layers bake up flat rather than doming is to use cake strips. Soak the cake strips in cold water before wrapping around the outside of the cake pan. This will ensure that the outside of the cake does not bake faster than the center, resulting in an evenly baked, flat cake.
Store this cake assembled in the fridge until ready to serve. Store individual slices wrapped tightly in plastic wrap at room temperature for up to 3 days or in the freezer for up to 3 months.
Baking in Grams
All of the recipes on this blog are carefully developed with gram measurements so you can easily recreate them in your own kitchen with success. Volume measurements are extremely inaccurate and leave room for significant errors. Not all measuring cups are made equally, so your one cup of flour will be different from my one cup of flour. By providing precise measurements in grams (aside from minor ingredients, which are given in tsp/tbsp), you can make these recipes accurately and with less cleanup! All you need is this kitchen scale.
If this still isn't enough to convince you, I have provided volume measurements in the recipe card. If you are interested in understanding the conversions, this is the best conversion chart.
But trust me, once you try baking in grams you'll never turn back!
Happy baking! x
Other cakes & cupcakes to try
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📖 Recipe
Dark Chocolate Mousse Cake
Ingredients
For the chocolate cake:
- 160 g (1 ⅓ cups) all-purpose flour
- 224 g (1 cup + 2 tbsp) granulated sugar
- 21 g (¼ cup) dutch process cocoa powder
- 21 g (¼ cup) black cocoa powder
- 1 teaspoon baking powder
- ¼ teaspoon salt
- 150 g (⅔ cup) whole milk, room temp
- 100 g (½ cup) neutral oil
- 2 eggs, room temp
- 1 teaspoon vanilla extract
- 75 g (⅓ cup) freshly brewed hot coffee or espresso
For the dark chocolate mousse:
- 227 g (1 ⅓ cups) dark chocolate
- 283 g (1 ¼ cups) heavy cream, divided
- 1 egg, room temp
- 1 teaspoon vanilla extract
- ¼ teaspoon salt
For the chocolate ganache
- 150 g (⅔ cup) heavy cream
- 85 g (½ cup) dark chocolate
Instructions
For the chocolate cake:
- Preheat the oven to 350 degrees F and line a 9" square pan with parchment paper.
- Soak cake strips in ice water.
- In a medium bowl, whisk together the flour, sugar, cocoa powders, baking powder, and salt. Set aside.
- In a large bowl, whisk together the milk, oil, eggs, and vanilla.
- Add the dry ingredients to the wet and whisk until just combined.
- Lastly, whisk in the hot coffee until fully combined.
- Pour the cake batter into the prepared pan and wrap the soaked cake strips around the outside of the pan. Bake for about 25 minutes or until a toothpick inserted comes out clean the cake pulls away from the sides of the pan.
- Allow the cake to cool in the pan completely. Cover with plastic wrap and set aside until ready to assemble.
For the dark chocolate mousse:
- In a medium bowl, add the chocolate and set aside.
- In a small saucepan, bring 170g (¾ cup) heavy cream to a simmer (or about 190 degrees F), then pour over the chocolate and mix until smooth.
- Whisk in the egg, vanilla, and salt until fully combined.
- In a separate small bowl, add the remaining 113g (½ cup) heavy cream and use an electric mixer to beat until stiff peaks form.
- Add the whipped cream to the chocolate mixture and gently fold with a rubber spatula until fully combined.
- Pour into a shallow dish and press plastic wrap up against the surface and chill for at least one hour.
For assembly:
- Line a pullman pan with parchment paper.
- Cut the cooled cake in half, and each half into two layers, giving 4 layers measuring roughly 9x5. You may need to trim the sides to make them fit in the pan.
- Add the first cake layer to the bottom of the pan and top with ⅓ of the mousse. I used a 3 tablespoon cookie scoop and added 4 scoops to each layer.
- Repeat with the remaining cake layers and mousse. Set aside.
For the dark chocolate ganache:
- In a small saucepan, bring the heavy cream to a simmer (or about 190 degrees F), then remove from heat, add the chocolate, and mix until smooth.
- Pour the warm ganache over the assembled cake and spread into an even layer.
- Place the cake in the fridge uncovered and chill for at least two hours before serving.
Notes
- Use a cake strip to create a flat cake. Soak these wilton cake strips in ice water before starting the cake batter. Just before baking, wrap the cake strips around the pan. The cold temperature on the outside of the cake will prevent the edges from baking faster than the center, resulting in an evenly baked flat cake.
- Use a cookie scoop to portion the filing. To add an even amount of filling to each layer, use a cookie scoop. I used a 3 tablespoon scoop and added 4 scoops to each layer.
- Chill the cake for at least two hours. To ensure the mousse and ganache have thickened up and the cake cuts easily, chill it uncovered for at least two hours!
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