Introduction

This Dark Chocolate Mousse Cake is a decadent dessert combining a rich chocolate cake base with a silky, smooth chocolate mousse and topped with a glossy ganache. Perfect for special occasions or when you want to impress with a homemade treat.

A slice of rich chocolate cake with two layers is shown on a white speckled plate with a silver fork beside it. The bottom layer is a dark, moist chocolate cake with a rough texture, while the top layer is a smooth, creamy chocolate mousse with a lighter brown color. The slice is covered in a glossy, thick chocolate ganache that smoothly coats the side and top edges, creating a shiny surface. The background is a white marbled texture. 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
1/8 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 until combined.
Step 4: Sift the dry ingredients into the wet mixture, whisk gently until just incorporated. The batter will be thick.
Step 5: Add boiling water gently and whisk until combined. Batter will thin slightly. Do not overmix.
Step 6: Pour batter into the prepared pan and bake for 24 to 28 minutes, until a toothpick comes out clean.
Step 7: Cool cake in the pan 15 minutes, then remove 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 together off heat in a small saucepan.
Step 9: Heat over low heat, whisking constantly, until mixture reaches 170ºF (76ºC), about 8-10 minutes.
Step 10: Remove from heat and add dark chocolate and vanilla, whisk until smooth.
Step 11: Transfer mousse mixture to a bowl, cover with plastic wrap directly on the surface, and chill 1 to 1.5 hours until thickened.
Step 12: Line the bottom of the springform pan with parchment paper. Level cake if needed, place back in pan, and wrap sides with acetate or parchment paper sprayed with oil.
Step 13: Whip cold heavy cream to firm peaks. Gently fold whipped cream into the chilled mousse mixture in two additions until combined but not overmixed.
Step 14: Spread mousse over cake layer evenly and chill for at least 8 hours.
Step 15: For ganache, place chopped dark chocolate in a bowl. Heat heavy cream to a simmer and pour over chocolate. Let sit 4-5 minutes.
Step 16: Stir ganache gently until smooth. If needed, warm over simmering water until completely melted.
Step 17: Remove cake from fridge, unmold, peel acetate/parchment, and slide onto serving plate.
Step 18: Pour ganache over cake and spread to edges. Chill 10-15 minutes before serving to let ganache set.
Step 19: Slice and enjoy your rich, luscious dark chocolate mousse cake!

Tips & Variations

Use espresso powder to enhance the chocolate flavor without adding bitterness. It’s optional but recommended for depth.
If your mousse mixture hardens in the fridge, let it soften at room temperature before folding in whipped cream.
Wrap the cake sides with acetate or lightly oiled parchment to prevent mousse from sticking and create smooth edges.
For extra texture, sprinkle chopped toasted nuts or cacao nibs on the mousse layer before chilling.
Make sure the heavy cream for whipping is cold to achieve firm peaks more easily.

Storage

Store the cake covered in the refrigerator for up to 3 days. To maintain the mousse’s texture, keep it chilled until just before serving. Leftover cake can be gently reheated at room temperature for 10-15 minutes if too firm, but avoid microwaving to preserve texture.

How to Serve

A close-up of a single slice of chocolate cake on a white speckled plate, showing two main layers: a thick, rich dark brown chocolate cake layer on the left with a rough, crumbly texture, and on the right, a smooth, creamy milk chocolate mousse layer topped by a shiny, dark chocolate ganache coating that wraps around the side. A silver fork rests on the plate, with chocolate mousse smeared on its prongs. The plate sits on a white marbled texture surface, with a blurred white plate and cake slice 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 benefits from resting overnight in the refrigerator to allow the mousse to set properly and flavors to meld.

What if I don’t have a springform pan?

A removable-bottom cake pan or a regular cake pan lined with parchment paper will work. Just be careful when unmolding the cake to avoid breaking the mousse layer.