Aerial Chocolate Raspberry Sponge

Preheat your oven to 170°C/340°F. Line the bottom of a 20cm round cake tin with parchment paper. Do not grease the sides of the tin; the batter needs to grip the sides to rise properly.

Sift the cake flour and cocoa powder together three times. This aerates the dry ingredients to prevent clumps from deflating the egg foam later.

Combine eggs, caster sugar, and vanilla in a large heatproof bowl set over a pan of simmering water (bain-marie). Whisk constantly until the sugar dissolves and the mixture is warm to the touch (about 40°C/105°F).

Remove from heat and whisk on high speed using an electric mixer until the mixture has tripled in volume, is pale, and reaches the 'ribbon stage' (where a trail of batter stays on the surface for a few seconds before sinking). This takes about 5-7 minutes.

Gently fold the sifted flour and cocoa into the egg foam in three batches. Use a metal spoon or spatula to cut down the center and fold over the top. Be extremely gentle to retain the air bubbles.

Pour the batter into the prepared tin and bake immediately for 20-25 minutes. The cake is done when the top springs back when lightly pressed and the sides pull away slightly from the tin.

While the cake bakes, combine raspberries, granulated sugar, lemon juice, and water in a small saucepan. Simmer over medium heat until the fruit breaks down and the sauce thickens slightly, about 10 minutes. Strain half for a smooth drizzle, keep the other half chunky for filling. Let cool completely.

Once the cake is cool, remove from the tin. Slice horizontally into two layers. Spread the chunky raspberry compote in the middle. Top with the second sponge layer.

Dust the top with icing sugar and drizzle with the smooth raspberry coulis. Garnish with fresh raspberries before serving.