Ingredients

Step by step

1. Heat the oven to 180°C, fan 160°C, gas 4. Grease 3 x 18cm round sandwich tins and line the bases with baking paper.
2. For the cake, sift the flour, cocoa powder and baking powder into a large mixing bowl. Add the butter, sugar and eggs. Using an electric hand-held whisk, beat for 1-2 minutes until thoroughly combined, then beat in the melted dark chocolate.
3. Divide the mixture evenly between the tins. Bake for 25-30 minutes until risen and just firm to the touch. Cool in the tins for 10 minutes, then turn out on to a wire rack and let them cool completely.
4. For the buttercream, beat the butter and icing sugar in a large bowl until smooth and creamy, then beat in the cream. Transfer two thirds to another bowl; fold in the melted white chocolate. Fold the melted dark chocolate into half of the remaining buttercream and the milk chocolate into the rest. If needed, chill the buttercreams until they are all a spreadable consistency.
5. Sandwich the cakes together with some of the white chocolate buttercream. Cover the top and sides with a thin layer of more white chocolate buttercream to seal in the crumbs. Chill for 30 minutes.
6. Spread the dark, milk and nearly all the remaining white chocolate buttercream in three thick bands around the cake, to cover. Use a palette knife to smooth the bands of buttercream so they merge slightly. Use the rest of the white chocolate buttercream to cover the top of the cake, then decorate with chocolate curls. Chill until ready to serve. Remove from the fridge 30 minutes before serving.