A raspberry mousse chocolate cake made with a rich chocolate sponge base and a light raspberry mousse. This layered dessert combines deep chocolate flavor with a fresh raspberry finish and slices cleanly after chilling.
Preheat the oven to 350°F / 180°C (320°F convection / 160°C fan) and line an 8×8 inch (20×20 cm) cake pan with parchment paper. In a large mixing bowl, whisk 3 large eggs, 60 g granulated sugar, 50 g light brown sugar, and 1 tsp vanilla extract with a hand mixer until pale, fluffy, and slightly thickened.
Sift in 65 g all-purpose flour , 15 g unsweetened cocoa powder, 1 tsp baking powder, and ¼ tsp salt, then add ½ tsp instant coffee. Mix until just combined. Melt 75 g dark chocolate in the microwave, add it to the batter, and fold gently with a spatula until evenly incorporated.
Pour the batter into the prepared cake pan and smooth the top. Bake for 25 minutes, or until a toothpick inserted into the center comes out clean. Place the pan on a wire rack and let the chocolate sponge cool completely in the pan.
Puree 400 g fresh raspberries in a food processor until smooth, then strain through a fine-mesh sieve to remove the seeds. Transfer the raspberry puree to a small saucepan with 1 tbsp lemon juice and 100 g granulated sugar, then heat over medium heat until the sugar dissolves.
Meanwhile, soak 3 gelatine sheets in cold water for about 5 minutes, until softened. Squeeze out the excess water, add the gelatine to the warm raspberry mixture, and stir until fully dissolved. Remove from the heat and let it cool on a wire rack.
In a separate mixing bowl, whip 480 ml heavy cream until stiff peaks form. Gently fold the cooled raspberry mixture into the whipped cream in 3 batches, mixing carefully until smooth and fully combined.
Remove the cooled chocolate sponge from the pan and trim the borders. Place the sponge in a prepared cake mold lined with cling film, then spread the raspberry mousse evenly over the top.
Refrigerate the cake overnight, or until fully set. Remove the cake from the fridge, carefully take off the mold, decorate with fresh raspberries, then slice and serve chilled.
Notes
Whisk Until Pale and Fluffy: I like to whisk the eggs and sugars until they look pale and airy, which helps the sponge bake softer.Cool the Raspberry Mixture Well: Let the raspberry base cool properly before folding it into the cream because I find the mousse sets smoother this way.Chill Overnight: I like to refrigerate the cake overnight so the mousse firms up properly and the slices come out cleaner.