Name: Decadent Chocolate Mousse Cake Recipe
Prep time: 15 min
Cook time: 25 min
Total time: 4 h 40 min
Cuisine: French-inspired
Ingredients: ⅔ cup (95g) all-purpose flour; ⅓ cup (28g) cocoa powder; ½ tsp baking powder; ¼ tsp baking soda; ¾ cup (150g) granulated sugar; ¼ tsp salt; ¼ cup (60ml) sunflower oil; 1 large egg, lightly beaten; ¼ cup (60ml) full fat sour cream; ⅓ cup (80ml) warm milk; 1 tsp (5ml) pure vanilla extract; 5 oz (142g) bittersweet chocolate (70% cocoa), finely chopped; 2 oz (56g) milk chocolate, finely chopped; ⅔ cup (150ml) whole milk; 3 large egg yolks; ⅓ cup (65g) granulated sugar; pinch of salt; 1 ¼ cups (300ml) cold heavy 35% whipping cream

If you’ve ever dreamed of a dessert that perfectly balances rich chocolate flavor with a light, airy texture, then this Decadent Chocolate Mousse Cake Recipe is your new best friend. Combining a tender, moist chocolate cake base with a luxurious, velvety mousse topping, it’s a show-stopper that’s surprisingly easy to make. Whether it’s a special occasion or just a treat-yourself day, this cake delivers pure happiness in every bite.

Ingredients You’ll Need

The image shows a wooden surface with 13 clear glass bowls and containers arranged neatly, each holding different baking ingredients. There are two bowls with white flour and sugar, and two others with different types of chopped chocolate pieces, light brown and dark brown. There is a small bowl with white cream and another one with white granulated sugar, along with a bowl of cocoa powder. Four eggs are positioned in the center, surrounding a small bowl with white baking powder or soda. A clear measuring jug with light yellow oil is on the bottom left, and a few white containers of milk and cream complete the layout. The whole scene is organized in a neat grid pattern. photo taken with an iphone --ar 4:5 --v 7

These simple but essential ingredients come together to create a cake that is moist, chocolaty, and creamy. Each ingredient plays a crucial role, from the cocoa powder that adds depth to the tender flour-based cake, to the rich bittersweet chocolate that makes the mousse irresistible.

All-purpose flour (⅔ cup / 95g): Provides the cake’s delicate structure while keeping it soft and tender.
Cocoa powder (⅓ cup / 28g): Adds a bold chocolate flavor and deep color to the cake layer.
Baking powder (½ tsp): Helps the cake rise just enough for a light crumb.
Baking soda (¼ tsp): Works alongside the baking powder to create a perfect cake texture.
Granulated sugar (¾ cup / 150g): Sweetens the cake layer for just the right balance to the rich chocolate.
Salt (¼ tsp): Enhances and rounds out all the chocolate and sweet flavors.
Sunflower oil (¼ cup / 60ml): Keeps the cake moist while allowing it to stay light.
Egg (1 large, lightly beaten): Binds the ingredients and adds richness.
Full fat sour cream (¼ cup / 60ml): Adds subtle tang and extra tenderness to the cake crumb.
Warm milk (⅓ cup / 80ml): Moistens the batter, ensuring a smooth texture.
Pure vanilla extract (1 tsp / 5ml): Brings out complex flavor layers in both cake and mousse.
Bittersweet chocolate (5 oz / 142g, 70% cocoa): Forms the rich, intense base of the mousse topping.
Milk chocolate (2 oz / 56g): Adds creaminess and sweetness to the mousse.
Whole milk (⅔ cup / 150ml): Heated to create the luscious chocolate custard for the mousse.
Egg yolks (3 large): Give the mousse a silky, custard-like richness.
Granulated sugar (⅓ cup / 65g): Sweetens the custard and balances the chocolaty bitterness.
Pinch of salt: Just enough to make the chocolate flavors pop.
Cold heavy whipping cream (1¼ cups / 300ml, 35% fat): Whipped to soft peaks for a light, airy mousse texture.

TIP

You’ll find the full ingredient list, instructions, and print option in the recipe card below.

How to Make Decadent Chocolate Mousse Cake Recipe

Step 1: Prepare the Cake Base

Start by preheating your oven to 350°F and lining an 8×8-inch metal baking pan with parchment paper, letting the edges hang over the sides for easy removal later. Then, sift together the flour, cocoa powder, baking powder, and baking soda into a mixing bowl. Adding sugar and salt, whisk everything evenly to ensure your dry ingredients are perfectly combined. Creating a well in the center, gently add oil, beaten egg, sour cream, warm milk, and vanilla extract before whisking everything into a smooth, lump-free batter that’ll give you that tender cake texture we all love.

Step 2: Bake and Cool the Cake

Pour the batter into your prepared pan, spreading it out evenly with a spatula for a perfectly flat top. Bake for 20 to 25 minutes, testing with a skewer to ensure it comes out clean in the center. Once baked, set your cake on a wire rack to cool completely—this step is crucial for layering the mousse smoothly. If needed, trim the top to get a level surface but you might be delighted to find it bakes nice and flat naturally.

Step 3: Craft the Silky Chocolate Mousse

Chop your dark and milk chocolates finely and place them in a heatproof bowl. Warm the milk in a microwave or saucepan until it’s steaming hot to prepare the rich custard base. Whisk together egg yolks and sugar in a saucepan, then slowly blend in the hot milk. Cook gently over medium-low heat, stirring constantly, until the mixture thickens enough to coat the back of a spoon. Immediately pour this custard over your chopped chocolate, add a pinch of salt, and stir until the chocolate melts into a smooth, glossy mixture. Let this cool for about 10-15 minutes to reach the perfect temperature for folding.

Step 4: Whip and Fold the Cream

Whip the cold heavy cream until it forms medium peaks—when you lift your mixer, the cream should curl slightly without being too stiff. Gently fold one-third of the whipped cream into the chocolate custard to lighten it, then carefully fold in the remaining cream in two batches. This folding technique preserves the airy texture that makes this Decadent Chocolate Mousse Cake Recipe so irresistible. Spread the mousse evenly over your cooled cake in the pan, smoothing the top with a spatula.

Step 5: Chill and Finish

Place your assembled cake in the refrigerator for at least four hours to allow the mousse to set perfectly. When you’re ready to serve, loosen the sides from the pan using a spatula, and lift the cake out by the parchment overhang. For a final touch, dust the top with cocoa powder for that elegant, chocolatey finish.

How to Serve Decadent Chocolate Mousse Cake Recipe

A square tiramisu dessert is shown, divided into nine equal pieces with three rows and three columns. The top layer is a smooth, light brown cocoa powder dusting that covers the entire surface evenly. One piece is removed and placed slightly away from the main square, revealing soft layers inside with a creamy middle layer and a light brown base. A small spatula rests near the removed piece and a woman's hand is holding the spatula. Around the dessert, there is cocoa powder sprinkled on a white marbled textured surface. There are also a knife with a wooden handle on the right and a bowl with cocoa powder on the top right corner. photo taken with an iphone --ar 4:5 --v 7

Garnishes

This cake shines on its own, but adding fresh berries or a sprig of mint can brighten up the rich chocolate flavors and add a pop of color. Whipped cream or a drizzle of raspberry coulis works beautifully too, giving a balance of sweetness and tang that pairs wonderfully with the mousse.

Side Dishes

Keep sides simple to let the star shine—consider a light espresso or chilled dessert wine to complement the chocolaty richness. Vanilla ice cream or a scoop of berry sorbet provides a cool contrast that’s simply divine beside each slice.

Creative Ways to Present

For gatherings, try slicing this cake into elegant squares or small rounds using a cookie cutter to serve as bite-sized treats. You can even top each piece with a curl of chocolate or a sprinkle of chopped nuts to amp up the texture and presentation for your guests.

Make Ahead and Storage

Storing Leftovers

Wrap leftover cake tightly in plastic wrap or keep it in an airtight container in the fridge. It will stay fresh for up to 3 days with the mousse retaining its creamy texture beautifully.

Freezing

This Decadent Chocolate Mousse Cake Recipe freezes well. Wrap it securely in plastic wrap and aluminum foil before freezing. Thaw overnight in the fridge before serving to keep the mousse silky and the cake moist.

Reheating

Since this cake is best served chilled, reheating is not recommended. If you prefer, enjoy leftovers straight from the fridge or let it sit at room temperature for 15-20 minutes for the mousse to soften slightly before serving.

FAQs

Can I use different types of chocolate in this recipe?

Absolutely! While bittersweet and milk chocolate create a beautiful balance here, you can experiment with semisweet, dark, or even white chocolate to tailor the cake’s flavor to your liking.

Is it necessary to use sour cream in the cake batter?

Sour cream adds moisture and a slight tang that enhances the cake’s flavor and keeps it tender, but you can substitute with Greek yogurt or buttermilk if needed.

How do I know when the mousse is properly whipped and folded?

The cream should be whipped to medium peaks, meaning it holds its shape but is still soft and smooth. Folding carefully ensures you don’t lose the air you’ve whipped in, resulting in a light and fluffy mousse texture.

Can I make this cake gluten-free?

You can substitute the all-purpose flour with a gluten-free baking blend, but make sure it contains xanthan gum or a similar binder for the best results.

What’s the best way to slice this mousse cake?

Use a sharp knife dipped in hot water and wiped dry between slices. This technique helps keep clean cuts through the mousse without dragging or squishing the cake.

Final Thoughts

Trust me when I say this Decadent Chocolate Mousse Cake Recipe is a total game-changer for any chocolate lover. It’s elegant, impressive, and yet surprisingly approachable for bakers of any level. Give it a try and get ready to have friends and family coming back for seconds — it’s one of those desserts that just makes you feel special with every forkful.

Decadent Chocolate Mousse Cake Recipe

Ingredients You’ll Need