Introduction

This Dark Chocolate Mousse Cake combines a rich, moist chocolate cake base with a creamy, luscious mousse layer and a glossy chocolate ganache topping. It’s an elegant dessert perfect for chocolate lovers and special occasions.

The image shows a rich three-layer chocolate cake on a white round plate. The bottom layer is a dark, moist chocolate cake, about one-third of the cake's height. The middle layer is a smooth, creamy milk chocolate mousse, lighter in color than the bottom, making up another third. The top layer is a shiny, dark chocolate ganache that looks glossy and smooth, slightly dripping over the edges. A slice is being lifted with a silver cake server, showing clean, sharp edges and the distinct layers. The whole cake sits on a wooden table with a white marbled texture underneath. photo taken with an iphone --ar 4:5 --v 7

Ingredients

Chocolate Cake:

1 Cup (120g) All-Purpose Flour
½ Cup (42g) Dutch Cocoa Powder
1 Teaspoon Fine Espresso Powder (optional, but recommended)
¾ Teaspoon Baking Powder
½ Teaspoon Baking Soda
½ Teaspoon Fine Sea Salt
1 Cup (200g) granulated white 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

Chocolate Mousse:

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 (to be whipped), cold

Chocolate Ganache:

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 flour, Dutch cocoa powder, espresso powder, baking powder, baking soda, and salt together.
Step 3: In a large bowl, whisk together sugar, oil, sour cream, egg, and vanilla extract until well combined.
Step 4: Sift dry ingredients into the wet, ensuring to push cocoa lumps through the sieve. Gently whisk until nearly combined, then add boiling water and whisk just until smooth. The batter will thin out.
Step 5: Pour batter into the prepared pan and bake for 24 to 28 minutes, or until a toothpick inserted comes out clean. Cool in pan 15 minutes, then remove and cool completely.
Step 6: For the mousse, whisk heavy cream, whole egg, yolk, sugar, cocoa powder, espresso powder, and salt off heat in a saucepan until combined.
Step 7: Over low heat, whisk constantly until mixture reaches 170ºF (76ºC), about 8–10 minutes.
Step 8: Remove from heat, add chopped dark chocolate and vanilla, whisk until smooth. Cover surface with plastic wrap and chill for 1 to 1.5 hours until thickened.
Step 9: Line springform pan bottom with fresh parchment. Level the cooled cake top if needed, place cake back in pan, and wrap sides with acetate or lightly oiled parchment secured with tape.
Step 10: Whip cold heavy cream until firm peaks form. Gently fold whipped cream into chilled chocolate mixture in two additions until no white streaks remain. Do not overmix.
Step 11: Spread mousse evenly over cake layer and chill cake for at least 8 hours.
Step 12: To make ganache, place chopped dark chocolate in a heatproof bowl. Heat heavy cream to a low simmer (about 185ºF/85ºC), pour over chocolate, and let stand 4–5 minutes. Stir gently until smooth. If needed, warm over simmering water until fully melted.
Step 13: Remove cake from fridge, unmold, peel off acetate or parchment, and transfer to a serving plate.
Step 14: Pour ganache over the cake and spread to edges. Chill 10–15 minutes to set ganache before slicing and serving.

Tips & Variations

Adding espresso powder enhances the chocolate flavor but can be omitted if unavailable.
Use a cake collar or acetate to keep mousse edges neat and easy to unmold.
For extra richness, choose a dark chocolate with at least 60% cacao.
Let the cake come to room temperature before slicing for clean cuts.

Storage

Store the cake covered in the refrigerator for up to 3 days. Let it sit at room temperature for 20 minutes before serving. Leftover cake slices can be wrapped and frozen for up to 1 month; thaw in the fridge overnight. Reheat ganache set cake only to room temperature without direct heat to maintain texture.

How to Serve

A close-up of a slice of chocolate cake on a white marble plate, showing three layers: the top and bottom layers are dark, moist chocolate cake with a rough texture, while the middle layer is a thick, smooth milk chocolate mousse with small air bubbles. The cake is coated on the sides and top with a glossy dark chocolate ganache that reflects light softly. There is some smeared chocolate mousse on the plate near the cake, adding a casual, delicious look. The background is a white marbled texture. 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, it’s ideal to prepare the cake and mousse a day ahead to allow proper chilling and setting. The ganache can be made just before serving or a few hours ahead and chilled.

Is it safe to use raw eggs in the mousse?

This recipe cooks the egg mixture to 170ºF (76ºC), which reduces risk by gently heating the eggs. Make sure to monitor the temperature carefully for food safety.