Brooklyn blackout cake

To make the custard filling, put the egg yolks, sugar and cornflour in a large bowl and whisk until light and creamy. In a medium pan, heat the milk and cardamom over a medium heat until just coming to a simmer. Remove from the heat and pour onto the egg yolks, whisking to combine. Pour the mixture back into the pan and whisk constantly until the custard has thickened and is smooth. Scrape back into the bowl and add the chocolate, stirring until fully melted and combined. Press a sheet of clingfilm onto the surface of the custard to prevent a skin from forming and chill for at least 2 hours.

To make the sponge, lightly butter and line 3 x 20cm round cake tins and heat the oven to 180C/fan 160C/gas 4. In a large bowl, cream the butter and sugars together until light and fluffy. Add the vanilla and beat to combine. Meanwhile, in a separate bowl, mix together the flour, cocoa powder, baking powder and salt. Pour the coffee and milk together into a jug. Add the egg whites to the butter mixture, a little at a time, beating until fully combined before adding more. Add the flour mixture to the cake batter in three additions, alternating with the coffee mixture. Divide the batter evenly between the prepared cake tins and bake for 30-40 minutes, or until the cakes spring back to the touch and are coming away from the sides of the tins. Allow to cool in the tins for 10 minutes before turning out onto a wire rack to cool completely.

To make the frosting, put the butter, chocolate and honey into a heatproof bowl set over a pan of simmering water and heat, stirring occasionally, until fully melted. Remove from the heat and pour in the cream, stirring together. Cool until the mixture has thickened to a spreadable consistency.

To assemble the cake, use a serrated knife to slice a thin layer of sponge from the top of each cake, creating flat, even layers. Put the offcuts into a bowl and crumble to make crumbs.

Put one cake onto a serving plate and top with half of the cardamom custard, repeat with the second cake and custard, then top with the remaining cake. To finish, spread the frosting over the top and sides of the cake and carefully press the cake crumbs over the whole cake. Kept in a sealed container this cake will keep for up to three days.