The Ultimate Dark Chocolate Mousse Layer Cake

Indulge in the Best Dark Chocolate Cake for Special Occasions! If you are searching for the ultimate chocolate lover's dream, look no further than this decadent Dark Chocolate Mousse Layer Cake. This show-stopping dessert features four moist layers of rich chocolate cake filled with an airy, melt-in-your-mouth chocolate mousse and finished with a silky smooth ganache. Whether you need a professional-looking birthday cake or the perfect Valentine's Day dessert, this recipe delivers intense dark chocolate flavor in every single bite.

Why You'll Want to Make Dark Chocolate Mousse Layer Cake

• Decadent Texture: The combination of dense, moist cake and light, fluffy mousse creates a sophisticated contrast that rivals high-end bakeries.

• Professional Results at Home: The structured assembly process, including a dedicated crumb coat, ensures a polished and "show-stopping" final look.

• Make-Ahead Friendly: You can prepare the mousse and even the cake layers days in advance, making it a stress-free centerpiece for parties.

• Rich Dark Chocolate Flavor: By using high-quality ingredients like Ghirardelli 60% Bittersweet chips, this cake satisfies even the deepest chocolate cravings.

Ingredients - Here's What You'll Need

Steps to Make Chocolate Cake Layers

1. Preheat oven to 350°F. Spray four 9-inch round cake pans with non-stick baking spray with flour and line with parchment paper. Set the pans aside until ready to use. Whisk together all-purpose flour, sugar, baking powder, baking soda, salt, and cocoa powder in a large bowl. Set the bowl aside until ready to use.

2. In a medium-size bowl with a spout (I used my 4-cup Pyrex measuring cup), whisk together sour cream, vegetable oil, and large eggs.

3. Then, add the buttermilk and vanilla extract. Whisk until well emulsified.

4. Pour the wet ingredients into the dry ingredients. Then, stir them together with a silicone spatula until well combined.

5. Next, add very hot tap water and stir with the spatula until well combined.

6. Use a large ice cream scoop to divide the batter evenly among the prepared cake pans. Place two pans offset on the lower rack of the oven and the other two pans offset on the upper rack so that they are not directly above the pans below. Bake for 19-23 minutes or until a toothpick inserted in the center comes out clean.

7. Remove the pans from the oven and place on wire cooling racks. Allow the cakes to cool completely in the pans.

Steps to Make Chocolate Mousse

1. While the cakes are cooling, prepare the chocolate mousse. Place cocoa powder in a small bowl and whisk in very hot tap water. Set the bowl aside until ready to use.

2. Place chocolate chips in a microwave-proof bowl and heat for 30 seconds, stirring after each heating, until the chips are melted. This should take about 2-3 minutes. Pour the cocoa powder mixture into the melted chocolate and stir with a silicone spatula until well combined. Set aside and allow it to cool slightly while whipping the cream.

3. Place the cold heavy whipping cream, powdered sugar, and vanilla extract in a large bowl.

4. Use an electric hand mixer to beat on medium-high until medium peaks form. This should take 3-4 minutes. Medium peaks are between soft/loose peaks and stiff peaks.

5. Pour the chocolate mixture into the whipped cream.

6. Use a silicone spatula to gently fold the chocolate mixture into the whipped cream. Avoid over-mixing, which can deflate/thin out the mousse. Cover the bowl and refrigerate for at least 2 hours and up to two days. I like to refrigerate it overnight and assemble the cake the next day.

To Assemble the Dark Chocolate Mousse Layer Cake

1. Remove the cakes from the pans and peel the parchment off the bottoms. Remove about ½ cup of chocolate mousse from the bowl and set it aside for the crumb coat. Place one cake layer, right side up, on a cardboard cake round and about 1 ½ cups of chocolate mousse on top of the cake. Use an offset icing spatula to gently spread the mousse into an even layer. Then place a second cake layer, upside down, on top of the chocolate mousse and spread about 1 ½ cups of chocolate mousse on top of the cake. Place a third cake layer, right side up, and spread 1 ½ cups of mousse on top of it.

2. Place the fourth cake layer upside down on top of the chocolate mousse. Then, spread the reserved chocolate mousse all over the cake to create a crumb coat. Place the cake uncovered in the refrigerator for at least an hour, and up to four hours to thoroughly chill before topping with chocolate ganache.

Steps to Make Chocolate Ganache

1. You should make the ganache after you have assembled the cake because it will need time to set up in the refrigerator. Place chocolate chips in a medium microwave-proof bowl and pour heavy whipping cream over them. Heat in the microwave in 30-second intervals, stirring well with a silicone spatula after each heating, until the chocolate is melted. This should take about 2 minutes.

2. Once the chips are melted, switch to a small whisk to fully emulsify the ganache. Set the bowl aside for 20 minutes to allow it to cool, whisking the ganache every five minutes or so.

Steps to Finish the Cake

1. Once the ganache has cooled for about 20 minutes, remove the cake from the refrigerator. Spoon the ganache over the top of the cake, allowing it to slightly run down the sides of the cake. Take care not to let too much run down the sides at once, or it will pool up around the bottom of the cake.

2. Use an offset icing spatula, in an upwards motion, begin smoothing the ganache that has dripped down the sides of the cake. Continue spooning the ganache on the top and smoothing the drippings down the sides until you have used all of the ganache and the sides of the cake are completely covered. Use a damp paper towel to wipe away any excess ganache that has pooled around the bottom of the cake.

3. Sprinkle some shaved chocolate on top of the cake. Chill the cake uncovered for 4-6 hours before serving. Then, store in an airtight container in the refrigerator for up to five days.

Whether you're a seasoned baker or looking to tackle your first professional-style layer cake, this Dark Chocolate Mousse Cake is the ultimate reward. It perfectly balances the intensity of dark chocolate with the lightness of an authentic French-style mousse, ensuring it's never too heavy but always satisfying. This recipe isn't just a dessert; it's a centerpiece guaranteed to be the highlight of any dinner party or family gathering.

Frequently Asked Questions

Recipe Tips and Tricks

• High-Quality Cocoa Matters: Use Ghirardelli 100% Dutch Process Cocoa for a deeper color and smoother flavor, though regular cocoa powder can be used if preferred.

• Even Mousse Layers: To ensure your cake is level, divide your mousse into four separate bowls before you begin assembling: three larger portions for the layers and one smaller ½ cup portion for the crumb coat.

• The Perfect Shave: For professional-looking decor, run a vegetable peeler along the edge of a high-quality chocolate bar (like Lindt or Ghirardelli) to create elegant chocolate shavings for the top.

• Fold Gently: When combining the chocolate mixture with the whipped cream, use a silicone spatula to fold gently; over-mixing will deflate the air and result in a thin mousse.