Dark Chocolate Mousse Cake: Three Layers of Chocolate Perfection

Dark Chocolate Mousse Cake

This dark chocolate mousse cake is rich and deeply chocolatey, yet it stays surprisingly light on the fork. Three chocolate components come together in one dessert: a very moist chocolate cake base, a light and airy chocolate mousse made without gelatin, and a silky dark chocolate ganache poured over the top.

The recipe makes 9 servings, with about 1 hour of prep, 24 minutes in the oven, and 9 hours of cooling and chilling.

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In my own kitchen, this is the cake I bake when I want something that looks impressive but does not demand pastry chef hands. If you love fruit with chocolate, a raspberry mousse cake is a lovely flavor variation to try another time.

The Layers

The cake is built from three layers, and each one has a job to do.

The chocolate cake base. This layer was adapted from a chocolate cupcake recipe, and it uses Dutch process cocoa powder for a deep, rounded chocolate flavor. Even served cold from the fridge, it stays extremely moist, which is exactly what you want underneath a soft mousse.

The dark chocolate mousse. Light, airy, and melting in the mouth, this mousse contains no gelatin. It does include eggs for richness and stability, and here is the part I love most: the eggs are cooked directly in the saucepan, slow and low, right along with the mousse mixture.

There is no separate tempering step like you would use for custard style ice cream. If you need an eggless version, the source recipe includes one in the FAQ section near the end of that post.

The dark chocolate ganache. A silky smooth ganache finishes the cake and ties all of the chocolate flavors together.

Ingredient Notes

Full quantities and the complete method live in the recipe card at the end of the post. These notes explain why each ingredient is there, so you can shop and measure with confidence.

For the chocolate cake:

• 1 cup all purpose flour (120 g). Weigh it on a kitchen scale. Too much flour is the fastest way to a dry, dense cake instead of a light and moist one.
• 1/2 cup Dutch process cocoa powder (42 g). Natural cocoa is acidic and would not work with the amount of leaveners in this recipe, so Dutch process is the right choice.
• 1 teaspoon fine espresso powder, optional. It does not make the cake taste like coffee. It simply deepens the chocolate flavor.
• 3/4 teaspoon baking powder and 1/2 teaspoon baking soda. Used together, they give this cake the rise and the texture it needs.
• 1/4 teaspoon fine sea salt. Salt balances the flavors and keeps the sweetness in check.
• 3/4 cup plus 2 tablespoons white granulated sugar (175 g). Sweetness plus moisture.
• 1/3 cup plus 1 tablespoon neutral oil (80 g). Oil keeps the crumb light and moist.
• 1/3 cup full fat sour cream (76 g), room temperature. More moisture and a tender crumb.
• 1 whole large egg, room temperature. Structure for the crumb.
• 1 teaspoon pure vanilla extract. Flavor.
• 1/2 cup boiling water (113 g). The hot water blooms the espresso and cocoa powder and thins the batter.

For the chocolate mousse:

• 1 1/2 cups heavy cream (340 g). This portion is cooked with the mousse mixture.
• 1 whole large egg plus 1 large yolk. Richness and thickening power.
• 1/3 cup white granulated sugar (67 g). Light sweetness.
• 1/4 cup Dutch process unsweetened cocoa powder (21 g). Deep chocolate flavor.
• 1 teaspoon fine espresso powder. Again, it boosts the chocolate.
• 1/8 teaspoon fine sea salt. Enhances all the flavors.
• 6 ounces dark chocolate (170 g). Chocolate chips in the 60% to 70% range work beautifully.
• 1 teaspoon pure vanilla extract.
• 1 cup heavy cream (227 g), cold. This second portion is whipped and folded in at the end.

For the chocolate ganache:

• 5 ounces dark chocolate, 60% to 70% (141 g), finely chopped.
• 2/3 cup heavy cream (151 g).

Step By Step Instructions

Below you will find the step by step method with photos, and the detailed recipe card with every measurement and timing is at the end of the post.

How to make Chocolate Cake

1. Preheat the oven to 350F (180C). Grease and line a 9 inch (23 cm) springform pan with parchment paper.
2. In a medium bowl, whisk together the flour, Dutch process cocoa powder, espresso powder, baking powder, baking soda, and salt.
3. In a large bowl, whisk the sugar, oil, sour cream, egg, and vanilla until well combined.
4. Sift the dry ingredients into the wet ingredients, pushing any cocoa lumps through the sieve. Gently whisk until nearly combined. The batter will be thick at this point, and that is exactly right.
5. Add the boiling hot water and gently whisk until just combined. The batter will thin out. Do not overmix.
6. Pour the batter into the prepared pan and bake for 24 to 28 minutes, until a toothpick inserted in the center comes out clean. Ovens vary, so keep an eye on it.
7. Cool on a wire rack for 15 minutes, then remove the cake from the pan and let it cool completely at room temperature or in the fridge.

Tip

For an even, level cake layer, use a cake strip. If you do not have one, wet a tea towel with cold water, wring it out, and wrap it around the cake pan before baking. The cake bakes flatter, which makes the mousse layer easier to spread.

How to Make Chocolate Mousse

1. Off heat, in a small saucepan, whisk together the heavy cream, the whole egg, the yolk, sugar, cocoa powder, espresso powder, and salt until well combined.
2. Set the pan over low heat and whisk constantly until the mixture reaches 170F (76C). This takes about 8 to 10 minutes. Slow and steady keeps the eggs smooth.
3. Off heat, add the chocolate and vanilla and whisk until smooth and combined.
4. Transfer the chocolate mixture to a medium bowl and press a piece of plastic wrap directly onto the surface so no skin forms. Chill in the fridge for 1 to 1.5 hours, until thick and spreadable.
5. While the mousse chills, line the bottom of the springform pan with a fresh piece of parchment paper. If needed, level the top of the cooled cake with a serrated knife, then place the cake back into the pan. Wrap the sides with a 29 inch (74 cm) piece of acetate, also called a cake collar, and tape the ends so it does not unravel. Parchment paper works too, lightly sprayed with oil so the cake releases easily.
6. After 1 to 1.5 hours, remove the chocolate mixture from the fridge and give it a good mix. In a large bowl, whip the cold heavy cream with a hand mixer to firm peaks. Do not overmix. In 2 additions, gently fold the chocolate mixture into the whipped cream until no white streaks remain.
7. Spread the chocolate mousse over the cake layer and chill for at least 8 hours.

Tip

A cake collar gives you cleaner sides. If you use parchment paper instead, a light spray of oil helps the mousse release more easily.

When you are ready to serve, make the ganache. Place finely chopped chocolate or chocolate chips in a heatproof bowl. In a small saucepan over medium heat, bring the heavy cream to a low simmer, about 185F (85C).

Pour the hot cream over the chocolate and let it stand untouched for 4 to 5 minutes, then stir slowly with a silicone spatula until smooth.

If any chocolate has not melted, set the bowl over a small pot of simmering water and heat until completely smooth. Unmold the chilled cake, peel off the collar, and slide the cake onto a serving plate.

Pour the ganache over the top and spread it to the edges with an offset spatula. For a neat finish, chill the cake for 10 to 15 minutes so the ganache sets before you slice and enjoy.

Substitutions

• Cake: swap the full fat sour cream for full fat Greek yogurt.
• Cake: use avocado, vegetable, canola, refined coconut, or grapeseed oil in place of the neutral oil.
• Cake: fine espresso powder is highly recommended, but it can be left out completely if you do not have it.
• Cake: hot coffee can replace the boiling water.
• Mousse: the fine espresso powder can be omitted if it is not in your pantry.
• Mousse: a chopped dark chocolate bar works just as well as chips in the 60% to 70% range.

Storage

Keep the cake covered in the refrigerator for up to 5 days.

To freeze it, wrap individual slices in plastic wrap, then once they are completely frozen, move them into freezer bags. Thaw a slice in the fridge overnight or at room temperature before you eat it.

Expert Tips

• Weigh your ingredients on a kitchen scale. Baking by grams is more accurate than measuring by volume. The gram conversions in this recipe follow King Arthur’s Weight Chart.
• Use a cake strip for a flat cake layer, or make your own by dampening a tea towel with cold water and wrapping it around the pan.
• Cook the eggs for the mousse slowly over low heat and whisk continuously. This prevents scrambling and keeps the mixture perfectly smooth.

Did you try this recipe?

If you make this dark chocolate mousse cake, consider leaving a 5 star rating and a short review. Your feedback helps me and helps other readers decide whether to bake it too. Happy baking.

More Cakes & Cupcakes

If you enjoyed this cake, there is plenty more to bake. Browse the cake and cupcake recipes on the blog for more layer cakes, simple snack cakes, and everyday cupcakes that follow the same relaxed, carefully tested approach.

FAQs

Dark Chocolate Mousse Cake

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Dark Chocolate Mousse Cake This dark chocolate mousse cake is rich and deeply chocolatey, yet it stays surprisingly light on the fork. Three chocolate components come together in one dessert: a very moist chocolate cake base, a light and airy chocolate mousse made without gelatin, and a silky dark chocolate ganache poured over the top.

• Total Time: 624 min
• Yield: 9 1x

Ingredients

Scale 1x2x3x

Chocolate Cake
1 cup All-Purpose Flour
0.5 cup Dutch Cocoa Powder
1 teaspoon Fine Espresso Powder
0.75 teaspoon Baking Powder
0.5 teaspoon Baking Soda
0.25 teaspoon Fine Sea Salt
0.75 cup plus 2 tablespoons White Granulated Sugar
0.33 cup plus 1 tablespoon Neutral Oil
0.33 cup Full-Fat Sour Cream, room temperature
1 Whole Large Egg, room temperature
1 teaspoon Pure Vanilla Extract
0.5 cup Boiling Water

Chocolate Mousse
1.5 cups Heavy Cream
1 + 1 Whole Large Egg and Large Yolk
0.33 cup White Granulated Sugar
0.25 cup Dutch Cocoa Powder
1 teaspoon Fine Espresso Powder
0.125 teaspoon Fine Sea Salt
6 ounces Dark Chocolate
1 teaspoon Pure Vanilla Extract
1 cup Heavy Cream, cold

Chocolate Ganache
5 ounces Dark Chocolate
0.67 cup Heavy Cream

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Instructions

Chocolate Cake
1-Preheat oven to 350ºF (180ºC): Preheat oven to 350ºF (180ºC). Grease and line a 9-inch (23cm) springform pan with parchment paper.
2-In a small mixing bowl, whisk together: In a small mixing bowl, whisk together the flour, Dutch cocoa powder, fine espresso powder, baking powder, baking soda, and salt.
3-In a large bowl and using a: In a large bowl and using a hand whisk, whisk together sugar, oil, sour cream, egg and vanilla until well combined.
4-Sift in the dry ingredients, ensuring the: Sift in the dry ingredients, ensuring the cocoa powder lumps are pushed through the sieve. Gently whisk the dry and wet ingredients together until nearly incorporated. The batter will be thick at this point.
5-Add boiling hot water and gently whisk: Add boiling hot water and gently whisk until just combined. The batter will thin out a bit. Do not overmix.
6-Pour cake batter into your prepared pan: Pour cake batter into your prepared pan and bake for 24 to 28 minutes or until an inserted toothpick comes out clean. Timing can vary on your oven.
7-Cool on a wire rack for 15: Cool on a wire rack for 15 minutes, then remove the cake from the pan and let cool completely at room temperature or in the fridge.

Chocolate Mousse
8-In a small saucepan, and off heat,: In a small saucepan, and off heat, whisk together heavy cream, a whole egg, a yolk, sugar, cocoa powder, espresso powder, and salt until well combined.
9-Over low heat, and whisking constantly, heat: Over low heat, and whisking constantly, heat until the mixture reaches 170ºF (76ºC). It will take about 8 to 10 minutes.
10-Off heat, add chocolate and vanilla and: Off heat, add chocolate and vanilla and whisk until smooth and combined.
11-Transfer chocolate mixture to a medium bowl: Transfer chocolate mixture to a medium bowl and place a piece of plastic wrap directly on top to prevent a skin from forming. Chill the chocolate mousse mixture in the fridge for 1 to 1.5 hour, until thick and spreadable.
12-As the chocolate mousse is cooling, line: As the chocolate mousse is cooling, line the bottom of your springform pan with a fresh piece of parchment paper. If needed, level off the top of the cake with a serrated knife. Next, place cooled chocolate cake back into the springform pan. Wrap the sides of the cake with a 29-inch (74cm) long piece of acetate (cake collar). Tape the acetate together at the ends to prevent it from unraveling. You can also use parchment paper. Just lightly spray it with oil to make it easier to release the cake.
13-After 1 to 1: After 1 to 1.5 hours, remove the chocolate mixture from the fridge and give it a good mix. Once it has thickened into a spreadable consistency, whip your cream. In a large mixing bowl, and using a hand mixer, whip cold heavy cream until firm peaks. Do not overmix. Then in 2 additions, gently fold the chocolate mixture and whipped cream together until there are no more white streaks. Do not overmix.
14-Spread the chocolate mousse on top of: Spread the chocolate mousse on top of the cake layer. Chill for at least 8 hours.

Chocolate Ganache
15-When you’re ready to serve, make the: When you’re ready to serve, make the chocolate ganache. Place finely chopped chocolate from a bar or chocolate chips in a heatproof medium bowl.
16-In a small saucepan, and over medium: In a small saucepan, and over medium heat, bring heavy cream to a low simmer until it reaches about 185ºF (85ºC). Submerge hot cream over the chocolate and let stand untouched for 4 to 5 minutes. Using a silicone spatula, slowly stir until smooth and combined. If the chocolate hasn’t completely melted, place the bowl of ganache over a small pot of simmering water. Heat until completely smooth.
17-Remove the chilled cake from the fridge: Remove the chilled cake from the fridge and unmold it from the pan. Peel off the acetate/parchment paper and then slide the cake onto a serving plate.
18-Pour the chocolate ganache on top of: Pour the chocolate ganache on top of the cake and using an offset spatula, spread it to the edges. Before serving, you can place the cake back into the fridge for 10 to 15 minutes to let the ganache set. Slice and enjoy!

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• Prep Time: 60 min
• Cook Time: 24 min
• Method: bake