Introduction

This Dark Chocolate Mousse Cake is a rich and decadent dessert perfect for chocolate lovers. It features a moist chocolate cake base layered with a silky, creamy chocolate mousse and topped with a smooth ganache. Ideal for special occasions or whenever you crave something indulgent.

A slice of rich chocolate cake is shown on a white speckled plate with three layers: a dark, moist chocolate cake layer on the left, a thick, smooth, light brown chocolate mousse layer in the middle, and a glossy, darker chocolate ganache layer covering the mousse on the right. There is a silver fork resting on the plate with some chocolate mousse smeared on its prongs, hinting that a bite has been taken. The plate sits on a white marbled surface with a blurred white plate holding more cake in the background. 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 temp)

1 Whole Large Egg (room temp)
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 your oven to 350ºF (180ºC). Grease and line a 9-inch (23cm) springform pan with parchment paper.

Step 2: In a small bowl, whisk together the 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 extract until well combined.
Step 4: Sift the dry ingredients into the wet mixture, pushing through any cocoa lumps. Gently mix until almost fully incorporated; the batter will be thick.

Step 5: Add boiling water and whisk gently until the batter thins. Avoid overmixing.
Step 6: Pour batter into the prepared pan and bake for 24-28 minutes, or until a toothpick inserted comes out clean.
Step 7: Cool the cake on a wire rack for 15 minutes. Remove from the pan and let it cool completely at room temperature or in the fridge.

Step 8: For the mousse, whisk together heavy cream, whole egg, yolk, sugar, cocoa powder, espresso powder, and salt in a small saucepan off the heat until combined.
Step 9: Over low heat, whisk constantly until the mixture reaches 170ºF (76ºC), about 8-10 minutes.
Step 10: Remove from heat, add dark chocolate and vanilla extract, whisk until smooth.

Step 11: Transfer to a bowl, cover surface with plastic wrap to prevent skin, then chill for 1 to 1.5 hours until thick and spreadable.
Step 12: Prepare the cake pan: line bottom with fresh parchment. Level cake top if needed, place cake in pan, and wrap sides with acetate or lightly oiled parchment paper to help release.
Step 13: Whip cold heavy cream until firm peaks form. Gently fold the chilled chocolate mixture into the whipped cream in two additions until fully combined without streaks.

Step 14: Spread the mousse evenly over the cake layer and chill for at least 8 hours to set.
Step 15: To make ganache, place chopped dark chocolate in a heatproof bowl. Heat heavy cream to just simmering (about 185ºF/85ºC) and pour over chocolate. Let sit 4-5 minutes, then stir gently until smooth. If needed, warm gently over simmering water until fully melted.
Step 16: Remove cake from fridge, unmold, and peel off acetate or parchment. Transfer to a serving plate.

Step 17: Pour ganache over the cake and spread evenly to the edges. Chill for 10-15 minutes before slicing and serving.

Tips & Variations

Use espresso powder to enhance the chocolate flavor without adding coffee taste; it’s optional but recommended.
For a different twist, add a layer of fresh raspberries between the cake and mousse for a fruit contrast.

Make sure your eggs and sour cream are at room temperature for a smoother batter and mousse texture.
If you don’t have acetate, parchment paper sprayed lightly with oil works well to release the mousse from the pan.

Storage

Store the cake covered in the refrigerator for up to 3 days. The mousse and ganache keep best chilled. When ready to serve, let the cake sit at room temperature for 10-15 minutes to soften slightly before slicing.

How to Serve

A close-up of a sliced chocolate cake with three visible layers: a dark, moist chocolate base at the bottom with a rough texture, a smooth and creamy light chocolate mousse layer in the middle, and a shiny, dark chocolate ganache layer on top with a glossy finish. The slice in front shows the thickness of each layer clearly, resting on a white marbled board with a wooden side visible. The cake is cut into even triangular pieces with clean edges, showing a rich and smooth finish on the ganache. 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 improves after resting. Make it a day ahead to allow the mousse to set properly and flavors to meld.

Can I use a different type of chocolate?

You can substitute the dark chocolate with semi-sweet or bittersweet varieties, but using good-quality chocolate with 60-70% cocoa content will give the best flavor and texture.