Method

• 1.
  Preheat oven to 170°C. Grease two 20cm round cake pans and line the base and sides with baking paper. Line a wire rack with baking paper.
• 2.
  For the chocolate sponge sift flours and cocoa into a bowl and set aside. Place eggs in the large bowl of a stand mixer with the whisk attachment and whisk for 5 minutes or until thick and tripled in volume. Gradually add sugar, whisking constantly, for 6-8 minutes until sugar has dissolved. Using a metal spoon, fold in flour mixture in 2 batches, folding all the way to the bottom to pick up any pockets of flour, then fold in butter and vanilla. Divide between prepared pans and bake for 30-35 minutes until a skewer inserted into the centre comes out clean. Cool in pan for 5 minutes, then turn onto a lined wire rack to cool completely.
• 3.
  To make the mousse, place chocolate in a heatproof bowl set over a saucepan of simmering water (don’t let the bowl touch the water) and stir until melted and smooth. Cool slightly.
• 4.
  Soak gelatine in cold water for 5 minutes to soften. Place 150ml cream in a small saucepan over low heat and bring to a simmer. Squeeze excess water from gelatine and stir into cream until melted and combined. Set aside to cool, then beat into chocolate mixture.
• 5.
  Place 500g strawberries in a blender with 80g icing sugar and whiz until smooth. Strain through a fine sieve, then beat into chocolate mixture.
• 6.
  Whisk remaining 300ml cream to stiff peaks in a bowl and set aside. Beat one-third of the whipped cream into chocolate mixture, then fold remaining cream in, in 2 batches. Pour into a bowl and chill overnight until set. When ready to serve, toss remaining 250g strawberries in a bowl with extra icing sugar.
• 7.
  For the frosting, place butter and sugar together in the bowl of a stand mixer with the paddle attachment and beat until pale. Beat in vanilla and cocoa and set aside.
• 8.
  To assemble, cut each cake in half horizontally. Place 1 cake on a serving platter and top with one-third of the mousse. Repeat layering, finishing with a layer of cake. Spoon over frosting and macerated strawberries to serve.