Chocolate Strawberry Mousse Cake

Chocolate Strawberry Mousse Cake combines the rich depth of chocolate sponge with the light, fruity essence of strawberry mousse for a dessert that balances decadence with freshness. This elegant layered cake features a moist dark chocolate base split into two layers, sandwiching a delicate strawberry mousse filling that sets to perfection. The contrasting textures and complementary flavors create a sophisticated dessert perfect for special occasions while remaining surprisingly achievable for home bakers.

I've made this cake countless times for family birthdays and dinner parties. My sister-in-law, who typically avoids sweet desserts, requests this specifically because the strawberry mousse cuts through the richness so beautifully. Last summer, I served it at an outdoor gathering and despite the heat, the mousse held its structure perfectly.

Ingredients:

For the chocolate cake:

• Flour (90g/3/4 cup): The foundation of our cake structure, use all-purpose for the right texture balance
• Sugar (170g/3/4 cup): Provides sweetness and helps create a tender crumb when it dissolves during baking
• Cocoa powder (35g/1/3 cup): Use Dutch-processed for a deeper chocolate flavor and richer color
• Baking soda (3/4 tsp) and baking powder (3/4 tsp): These leavening agents work together to create a light, airy texture
• Salt (1/2 tsp): Enhances the chocolate flavor and balances sweetness
• Egg (1): Provides structure and richness to the cake
• Milk (125ml/1/2 cup): Adds moisture and helps activate the leavening agents
• Vegetable oil (60ml/1/4 cup): Creates a moister cake than butter would and keeps it softer when refrigerated
• Vanilla (1 tsp): Enhances the chocolate flavor with warm, aromatic notes

For the strawberry mousse:

• Eggs (2 large, separated): Yolks add richness, whites create volume when whipped
• Superfine sugar (4 tbsp): Dissolves easily in the mousse, creating a smooth texture
• Strawberries (190ml/3/4 cup blended): Select fragrant, ripe berries for the best flavor or use frozen for convenience
• Gelatin (3 tsp) and water (3 tbsp): Essential for stabilizing the mousse so it holds its shape
• Double cream/whipping cream (250ml/1 cup): Creates the luxurious, light texture characteristic of mousse

For decoration:

• Double cream/whipping cream (125ml/1/2 cup): Whips to perfect piping consistency
• Icing sugar (2 tbsp): Sweetens and stabilizes the whipped cream
• Vanilla (1/2 tsp): Adds depth to the cream's flavor
• Fresh strawberries (3-4 halved): Choose bright red, firm berries for the most attractive presentation

Step-by-Step Cooking Instructions:

1. Prepare the Chocolate Cake

Begin by preheating your oven to 350°F/180°C. Properly prepare your 9-inch springform cake pan by thoroughly buttering the sides and lining the bottom with parchment paper, which prevents sticking and makes removal easier. In a large mixing bowl, thoroughly combine the dry ingredients (flour, sugar, cocoa powder, baking powder, baking soda, and salt), whisking to eliminate any lumps especially in the cocoa powder. In a separate bowl, whisk together the wet ingredients (egg, milk, oil, and vanilla) until completely smooth and uniform. Pour the wet mixture into the dry ingredients gradually, beating with an electric mixer on medium speed for about 2 minutes until the batter becomes smooth and slightly thickened. The batter should have a pourable consistency with a rich chocolate color.

2. Bake the Cake Base

Pour the prepared batter into your lined cake pan, using a spatula to ensure it's evenly distributed and the top is level. Place in the center rack of your preheated oven and bake for 25-30 minutes, watching carefully toward the end of baking time. The cake is ready when a toothpick inserted into the center comes out clean or with just a few moist crumbs attached. The top should spring back when lightly touched. Allow the cake to cool in the pan for exactly 10 minutes - this timing helps the cake set enough to handle but prevents it from sticking to the pan. Run a thin knife around the edges before removing from the pan, then transfer to a wire rack to cool completely, which typically takes about 1-2 hours.

3. Prepare the Strawberry Mousse

Begin by carefully separating the eggs, ensuring no yolk contaminates the whites (they won't whip properly if fat is present). Process your strawberries in a blender until completely smooth, straining if needed to remove seeds for a more refined texture. In a medium bowl, vigorously beat the egg yolks and sugar for about 3-4 minutes until the mixture becomes pale yellow and forms ribbons when the beater is lifted. Fold in the strawberry puree with a gentle hand to maintain the air incorporated during beating. In a small microwave-safe bowl, sprinkle the gelatin evenly over cold water and let stand for 5 minutes until it becomes spongy in texture. Microwave this mixture for 30-40 seconds until the gelatin fully dissolves but doesn't boil. Immediately whisk this warm gelatin mixture into the strawberry-egg yolk mixture until completely incorporated.

4. Complete the Mousse Assembly

In a separate clean bowl, whip the cream until it forms soft peaks that hold their shape but still have a slight glossy appearance - be careful not to overwhip. Using a large spatula, gently fold this whipped cream into the strawberry mixture with a down-and-over motion to maintain as much air as possible. In another clean, dry bowl with clean beaters, whip the egg whites until they form soft peaks that slightly bend at the tips when the beater is lifted. Carefully fold these whites into the mousse mixture with a light touch, continuing just until no white streaks remain visible. Let this mixture stand at room temperature for 10-15 minutes until it begins to thicken slightly but remains workable.

5. Assemble the Cake

Using a long, serrated knife held parallel to your work surface, carefully cut the completely cooled cake horizontally into two even layers. A slow sawing motion works best, and rotating the cake as you cut ensures even layers. Clean and reassemble your springform pan, placing the bottom cake layer back inside. Pour the partially set mousse over this bottom layer, using a spatula to ensure it's evenly distributed and reaches the edges. The mousse should be thick enough not to run but still spreadable. Refrigerate this half-assembled cake for exactly 1 hour until the mousse is firm enough to support the top layer. Carefully place the second cake layer on top of the set mousse, pressing very gently to secure it. Return the completed cake to the refrigerator for at least 2 more hours or overnight for the flavors to meld and textures to set completely.

6. Decorate and Serve

Just before serving, prepare the decoration by whipping the cream with icing sugar and vanilla until it forms stiff peaks that hold their shape when the beater is lifted. Transfer this cream to a piping bag fitted with a star tip. Release the springform pan sides carefully and transfer the cake to a serving plate. Arrange halved strawberries decoratively on top of the cake, positioning them to allow space for cream piping. Pipe decorative rosettes around the edge of the cake and anywhere else you'd like accent points. For the cleanest slices, use a large, sharp knife dipped in hot water and wiped clean between cuts. Serve chilled but allow to sit at room temperature for 15-20 minutes before eating for the best flavor experience.

I grew up watching my grandmother make strawberry preserves every summer, and this mousse cake has become my modern tribute to her dedication to showcasing fresh berries. My oldest son, typically a chocolate purist who avoids fruit-based desserts, made an exception for this cake on his 16th birthday last year. He said the strawberry flavor reminded him of our berry-picking adventures when he was little. I've found organic strawberries tend to have the most vibrant flavor in this recipe, though they're smaller and require more prep time.

Seasonal Adaptations

The beauty of this recipe lies in its adaptability throughout the year. In summer, when strawberries are at their peak, using fresh local berries creates an incomparably bright flavor profile that truly celebrates the season. The mousse takes on a natural rosy hue and intense strawberry aroma that store-bought berries simply can't match. During winter months, good-quality frozen strawberries work wonderfully once properly thawed and drained. For special occasions, I've experimented with adding a tablespoon of strawberry liqueur to the mousse for adults, which enhances the berry flavor and adds sophisticated complexity. Don't limit yourself to strawberries either – this same technique works beautifully with raspberries or a mixed berry blend, each creating its own unique color and flavor profile.

Troubleshooting Tips

Even experienced bakers occasionally encounter challenges with mousse cakes. If your mousse seems too loose after adding all ingredients, allow it to chill for 5-10 minutes before pouring onto the cake layer. Rushing this step can result in mousse that seeps into the cake rather than creating a distinct layer. Watch carefully when heating the gelatin – overheating causes it to lose its setting properties. If your whipped cream deflates quickly, try chilling the bowl and beaters beforehand and make sure your cream is very cold. For the chocolate cake, measure cocoa powder by spooning it into measuring cups rather than scooping directly from the container, which compacts it and results in too much powder. Room temperature eggs incorporate better into the mousse and create more volume when whipped. Lastly, patience is essential – this dessert truly benefits from proper setting time, so resist the urge to rush the chilling process.

Make-Ahead and Storage Advice

This mousse cake actually improves with time, making it perfect for advance preparation. The complete cake can be made up to two days before serving and kept refrigerated in the springform pan for protection. However, I recommend adding the whipped cream decoration and fresh strawberry garnish within a few hours of serving for the freshest appearance. Leftover cake will keep well for up to three days in the refrigerator in an airtight container, though the whipped cream decoration may begin to weep slightly. For elegant individual servings at dinner parties, I sometimes make this recipe in individual glass serving dishes instead of a cake format – simply crumble the baked chocolate cake into the bottom of each glass and top with strawberry mousse for stunning visual appeal without the need for cake cutting. The mousse portion can even be frozen for up to a month; thaw overnight in the refrigerator before assembling with fresh cake layers.

Recipe FAQs

→ Can I use frozen strawberries for the mousse?

Yes, frozen strawberries work well for the mousse. Just be sure to thaw them completely first and drain excess liquid before blending to avoid a runny texture. This makes it possible to enjoy this dessert year-round.

→ How far in advance can I make this cake?

You can prepare this cake up to 2 days in advance. Keep it refrigerated in the springform pan until a few hours before serving. Add the final whipped cream decoration and fresh strawberries just before serving for the best presentation.

→ Can I substitute the gelatin for a vegetarian option?

Yes, you can substitute the gelatin with agar-agar powder for a vegetarian alternative. Use about 1-1.5 teaspoons of agar-agar powder for every 3 teaspoons of gelatin. Follow package instructions for dissolving it properly.

→ How do I prevent the mousse from becoming runny?

Ensure proper setting by allowing the gelatin mixture to cool slightly before adding to other ingredients. When folding in the whipped cream and egg whites, be gentle to maintain air bubbles. Most importantly, let the mousse begin to set (10-15 minutes) before assembling the cake, and chill thoroughly for at least 3 hours total.

→ What's the best way to cut clean slices of this cake?

For clean slices, dip a long, sharp knife in hot water and wipe dry between each cut. This helps the knife glide through both the cake and mousse layers without dragging. Serve slices chilled for the best texture and flavor.

→ Is it safe to use raw eggs in the mousse?

The recipe notes that the eggs are tempered by the hot gelatin mixture but aren't fully cooked. For safety, use fresh, high-quality eggs (free-range or organic as suggested). If concerned, you can use pasteurized eggs or egg products specially designed for uncooked applications.