Chocolate Sponge

1. Preheat the oven to 160C/320F and line the bottom of an 8-inch cake tin
2. Separate the eggs, put the egg whites in a large mixing bowl and the egg yolks in a medium mixing bowl
3. Add the milk and vegetable oil to the egg yolks and whisk to combine
4. Sift in the cocoa powder and cake flour and mix until smooth
5. Whisk the egg whites with an electric mixer or stand mixer until it reaches soft peaks, add the sugar and continue to whisk until stiff peaks
6. Add 1/3rd of the egg whites to the chocolate mixture and mix until smooth
7. Add the chocolate mixture to the egg whites and gently fold with a rubber spatula until combined
8. Pour the cake batter into the prepared pan and bake for 20 minutes, or until cooked through and a toothpick inserted in the centre emerges clean
9. Remove from the oven and cool completely on a wire rack
10. Line the sides of a 6-inch cake ring or springform tin with a sheet of acetate or baking paper
11. Cut out a 6-inch circle from the cooled cake with a thin knife and place it at the bottom of the lined cake ring

Dark Chocolate Mousse

1. Place all three gelatine sheets in a bowl of iced water to bloom
2. Combine the dark chocolate and milk in a heatproof bowl and stir until smooth
3. Squeeze the water from one sheet of gelatin and add it to the warm chocolate mixture
4. Mix until completely dissolved
5. In a medium bowl whip the cream, or in the bowl of a stand mixer fitted with a whisk attachment until soft peaks form
6. Add the chocolate and fold until completely combined
7. Pour the mousse over the sheet of chocolate cake at the bottom of the cake ring
8. Place the cake in the fridge to set for 15-20 minutes while you prepare the next layer

Milk Chocolate Mousse

1. Repeat the steps above with the milk chocolate and pour it over the bottom layer
2. Place in the fridge to set for another 15-20 minutes while you prepare the final layer

White Chocolate Mousse

1. Repeat the steps again with white chocolate and pour it over the middle layer
2. Place it in the fridge to set for 1-2 hours or until completely set

Assembly

1. Once chilled remove the cake from the cake tin and peel off the acetate or baking paper
2. Dust with cocoa powder the top layer with cocoa powder and enjoy chilled