Make this impressive chocolate ganache drip cake with Swiss meringue buttercream for a special occasion. Crumb coat cake three 20cm round cake tins and line with non-stick baking paper.
Beat the butter and sugar together in a large bowl until light and smooth. Gradually beat in the eggs until combined, then mix in the vanilla. Fold in the flour and baking powder until everything is combined. Stir in the milk to loosen. Bake the sponges for 20 mins until golden and a skewer inserted into the centre comes out clean. Leave to cool in the tins for 10 mins, then transfer onto a wire rack to cool completely.
Meanwhile, make the Swiss meringue buttercream. Put the egg whites and sugar into a heatproof bowl over a small pan of gently simmering water. Make sure the bowl doesn’t touch the water. Whisk for 3-4 mins until the sugar dissolves.
Put into an electric mixer and whisk for 10 mins over a medium-high speed until you have a thick meringue. Gradually add the butter into the meringue mixture for 5 mins until incorporated and the buttercream is fluffy. Put one sponge onto a plate or cake stand, top it with a few tablespoons of the buttercream and spread into an even layer. Add the next sponge, and repeat. Chill in the fridge for 45 mins. Remove and smooth a thick layer of the remaining buttercream around the cake using a palette knife, reserving a little for decoration.