Introduction

This Dark Chocolate Mousse Cake is a decadent treat that combines a rich, moist chocolate cake with a smooth, creamy chocolate mousse topping. Finished with a glossy chocolate ganache, it’s a perfect dessert for chocolate lovers and special occasions alike.

A slice of dark chocolate cake with three layers is shown on a white speckled plate placed on a white marbled surface. The bottom layer is rich dark chocolate cake with a crumbly texture, the middle layer is a smooth, light brown chocolate mousse, and the top layer is a thick, shiny chocolate ganache coating. A fork resting on the plate has some chocolate mousse on it. In the background, there is a white plate with another piece of cake slightly out of focus. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

1 Cup (120g) All-Purpose Flour
½ Cup (42g) Dutch Cocoa Powder
1 Teaspoon Fine Espresso Powder (optional)
¾ Teaspoon Baking Powder
½ Teaspoon Baking Soda
¼ Teaspoon Fine Sea Salt
¾ Cup + 2 Tablespoons (175g) White Granulated Sugar
⅓ Cup + 1 Tablespoon (80g) Neutral Oil (avocado, vegetable, canola)
⅓ Cup (76g) Full-Fat Sour Cream (room temperature)
1 Whole Large Egg (room temperature)
1 Teaspoon Pure Vanilla Extract
½ Cup (113g) Boiling Water
1 ½ Cups (340g) Heavy Cream
1 Whole Large Egg + 1 Large Yolk
⅓ Cup (67g) White Granulated Sugar
¼ Cup (21g) Dutch Cocoa Powder
1 Teaspoon Fine Espresso Powder
⅛ Teaspoon Fine Sea Salt
6 Ounces (170g) Dark Chocolate
1 Teaspoon Pure Vanilla Extract
1 Cup (227g) Heavy Cream (cold, to be whipped)
5 Ounces (141g) Dark Chocolate (60% to 70%)
⅔ Cup (151g) Heavy Cream

Instructions

Step 1: Preheat oven to 350ºF (180ºC). Grease and line a 9-inch (23cm) springform pan with parchment paper.
Step 2: In a small bowl, whisk together flour, Dutch cocoa powder, espresso powder, baking powder, baking soda, and salt.
Step 3: In a large bowl, whisk sugar, oil, sour cream, egg, and vanilla until well combined.
Step 4: Sift the dry ingredients into the wet mixture, gently whisking until nearly combined. The batter will be thick.
Step 5: Add boiling water and whisk gently until just combined. The batter will thin out. Do not overmix.
Step 6: Pour batter into prepared pan and bake 24–28 minutes, or until a toothpick inserted comes out clean.
Step 7: Cool cake in pan for 15 minutes, then remove from pan and cool completely on a wire rack or in the fridge.
Step 8: For the mousse, whisk heavy cream, whole egg, yolk, sugar, cocoa powder, espresso powder, and salt in a saucepan off heat until combined.
Step 9: Heat mixture over low heat, whisking constantly, until it reaches 170ºF (76ºC), about 8–10 minutes.
Step 10: Remove from heat, add dark chocolate and vanilla, whisk until smooth. Cover with plastic wrap directly on surface and chill 1–1.5 hours until thickened.
Step 11: Line bottom of springform pan with parchment. Level cake if needed, place back in pan, and wrap sides with acetate or oiled parchment paper.
Step 12: Whip cold heavy cream to firm peaks. Gently fold whipped cream into the chilled chocolate mixture in two additions until no white streaks remain.
Step 13: Spread mousse evenly over cake layer and chill at least 8 hours.
Step 14: For ganache, place chopped dark chocolate in heatproof bowl.
Step 15: Heat heavy cream in saucepan until low simmer (~185ºF/85ºC). Pour over chocolate, let stand 4–5 minutes, then stir gently until smooth. Warm over simmering water if needed to melt fully.
Step 16: Remove cake from fridge, unmold, and peel off acetate/parchment. Place cake on serving plate.
Step 17: Pour ganache over cake, spreading to edges. Chill 10–15 minutes to set ganache before slicing and serving.

Tips & Variations

Use espresso powder to enhance the chocolate flavor, but it’s optional if you prefer a pure chocolate taste.
For a dairy-free version, substitute heavy cream with coconut cream and use dairy-free chocolate.
Wrap the sides with acetate for a clean mousse edge; parchment paper lightly oiled works as a substitute.
Let the mousse soften slightly at room temperature if it becomes too firm after chilling before folding in the whipped cream.

Storage

Store the mousse cake in an airtight container in the refrigerator for up to 4 days. Let it sit at room temperature for 10–15 minutes before serving to soften the mousse. Ganache may firm up when chilled but will soften nicely as it warms.

How to Serve

The image shows a rich chocolate cake with three clear layers: a dark, dense chocolate base, a thick middle layer of smooth chocolate mousse in a lighter brown shade, and a shiny, glossy chocolate glaze on top that gently drips down the sides. The cake is sliced, and one triangular piece is lifted with a silver spatula, showing the smooth textures clearly. The cake sits on a round white plate placed on a white marbled surface, with a few stacked white plates blurred in the background. Photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I make this cake ahead of time?

Yes, this cake actually benefits from chilling overnight or longer to allow the mousse to set fully and flavors to meld. Just keep it refrigerated until ready to serve.

What if I don’t have a springform pan?

A springform pan is ideal for easy removal of the cake without damaging the mousse layers. If unavailable, use a regular cake pan lined generously with parchment paper and carefully invert the cake to remove after chilling.