Name: Dark Chocolate Mousse Cake Recipe
Prep time: 30 min
Cook time: 23 min
Total time: 4 h 53 min
Cuisine: American
Ingredients: 1 and 3/4 cups (219g) all-purpose flour (spooned & leveled); 1 and 3/4 cups (350g) granulated sugar; 3/4 cup (64g) unsweetened natural cocoa powder; 2 teaspoons espresso powder (optional); 2 teaspoons baking soda; 1 teaspoon baking powder; 1 teaspoon salt; 3/4 cup (180g) full-fat sour cream, room temperature; 1/2 cup (113g/120ml) vegetable oil; 2 large eggs, room temperature; 1/2 cup (120g/ml) buttermilk, room temperature; 2 teaspoons pure vanilla extract; 1/2 cup (120g/ml) hot water or black coffee; 1 cup (170g) semi-sweet mini chocolate chips tossed in 1 Tbsp flour (optional); 1/2 cup (120g/ml) hot water; 1/4 cup (21g) unsweetened natural or Dutch-process cocoa powder; 8 ounces (226g) quality semi-sweet chocolate, finely chopped; 2 cups (480g/ml) heavy cream, cold; 2 Tablespoons confectioners’ sugar; 1/2 teaspoon pure vanilla extract; 8 ounces (226g) quality semi-sweet chocolate, finely chopped; 1 cup (240g/ml) heavy cream; Fresh berries and/or chocolate shavings

Jump to Recipe

Introduction

This Dark Chocolate Mousse Cake is a rich and decadent dessert that combines moist chocolate layers with silky chocolate mousse and a smooth ganache finish. Perfect for special occasions or whenever you crave an indulgent treat.

A close-up view of a dark chocolate layer cake slice showing four thick, moist chocolate cake layers separated by three creamy light brown chocolate frosting layers. The top layer is covered with a smooth, glossy dark chocolate ganache, and a single bright red raspberry sits on top as decoration. The cake slice is held on a silver cake server, placed on a white marbled surface with a blurred rustic brown background. Another raspberry is softly visible in the background off to the side. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

1 and 3/4 cups (219g) all-purpose flour (spooned & leveled)
1 and 3/4 cups (350g) granulated sugar
3/4 cup (64g) unsweetened natural cocoa powder
2 teaspoons espresso powder (optional)
2 teaspoons baking soda
1 teaspoon baking powder
1 teaspoon salt
3/4 cup (180g) full-fat sour cream, at room temperature
1/2 cup (113g/120ml) vegetable oil
2 large eggs, at room temperature
1/2 cup (120g/ml) buttermilk, at room temperature
2 teaspoons pure vanilla extract
1/2 cup (120g/ml) hot water or black coffee
1 cup (170g) semi-sweet mini chocolate chips tossed in 1 Tbsp flour (optional)
1/2 cup (120g/ml) hot water
1/4 cup (21g) unsweetened natural or Dutch-process cocoa powder
8 ounces (226g) quality semi-sweet chocolate, finely chopped
2 cups (480g/ml) heavy cream, cold
2 Tablespoons confectioners’ sugar
1/2 teaspoon pure vanilla extract
8 ounces (226g) quality semi-sweet chocolate, finely chopped (for ganache)
1 cup (240g/ml) heavy cream (for ganache)
Optional, for garnish: fresh berries and/or chocolate shavings

Instructions

Step 1: Preheat the oven to 350°F (177°C). Grease four 8-inch or 9-inch cake pans, line with parchment paper rounds, then grease the parchment. This helps the cakes release easily.
Step 2: In a large bowl, whisk together the flour, sugar, cocoa powder, espresso powder (if using), baking soda, baking powder, and salt. Set aside.
Step 3: In another large bowl, use a mixer or whisk to combine sour cream, oil, and eggs on medium-high speed until blended. Add buttermilk and vanilla, mixing until combined.
Step 4: Pour the dry ingredients into the wet mixture. Add hot water or coffee and mix on low speed until just combined. Fold in the floured mini chocolate chips if using. Divide the batter evenly between the prepared pans.
Step 5: Bake for 19–23 minutes, until a toothpick inserted in the center comes out clean. Cool the cakes in the pans on a rack for 1 hour. Loosen edges with a knife, remove from pans, peel off parchment, and let cool completely. Expect slight sinking in the middle.
Step 6: To make the mousse, whisk hot water and cocoa powder until smooth. Melt 8 ounces of chopped chocolate in a double boiler or in 20-second microwave increments, stirring until smooth. Stir the cocoa mixture into the melted chocolate; set aside.
Step 7: Whip 2 cups cold heavy cream, confectioners’ sugar, and vanilla with a mixer on medium-high until medium peaks form (about 3 minutes). Gently fold chocolate mixture into whipped cream until combined. Refrigerate mousse for at least 2 hours or up to 2 days.
Step 8: Level the cooled cakes if needed by slicing a thin layer off the tops. Place one cake layer on a serving plate. Spread about 1.5 cups of chocolate mousse evenly over the top. Repeat layering and spreading mousse with the second and third layers, topping with the final cake layer.
Step 9: Spread the remaining mousse as a crumb coat over the sides and top of the cake. Smooth with a bench scraper. Refrigerate for 1 to 4 hours while preparing the ganache.
Step 10: Make the ganache by placing the chopped chocolate in a heat-proof bowl. Heat 1 cup heavy cream just until simmering, then pour over chocolate. Let sit 2–3 minutes, then stir gently until smooth. Refrigerate for 30 minutes to 1 hour to thicken.
Step 11: Pour or spoon the ganache over the chilled cake, smoothing the top and sides with a spatula. Garnish with fresh berries or chocolate shavings if desired. Serve immediately or chill uncovered for 4–6 hours before serving.

Tips & Variations

Use black coffee instead of water in the cake batter for a deeper chocolate flavor.
Surface the mousse carefully to avoid deflating it and preserve its light texture.
For easier slicing, chill the cake thoroughly before cutting.
Try adding a hint of chili powder or cinnamon to the cake batter for a subtle spice twist.

Storage

Store leftover cake tightly covered in the refrigerator for up to 5 days. Bring to room temperature before serving for best flavor and texture. Ganache can firm up in the fridge, so let the cake sit out for 20–30 minutes before slicing.

How to Serve

A tall, round chocolate cake with four visible dark, moist cake layers separated by smooth, light brown chocolate frosting layers sits on a wooden stand with bark edges. The outside of the cake is covered in a thick layer of shiny, smooth milk chocolate frosting. On top of the cake, there are several fresh blackberries and raspberries placed around a small light pink flower. A small light pink flower also rests on the white marbled surface near the cake stand. The background shows a dark wooden 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 in advance?

Yes, you can prepare the cake layers, mousse, and ganache up to two days ahead. Assemble and refrigerate as directed. This helps the flavors meld and makes serving easier on your event day.

What if I don’t have sour cream or buttermilk?

You can substitute sour cream with an equal amount of Greek yogurt. For buttermilk, mix 1/2 cup milk with 1/2 teaspoon lemon juice or vinegar, let sit for 5 minutes before using.