This cupcake is based on a yeasted German cake that has a sponge base and a crumble-like topping. This kind of cake has many varieties and is often known as ‘coffee cake’ stateside, not necessarily because it contains coffee, but because it’s intended to be eaten alongside a cup of coffee! Confused? I was at first! Change the crumble topping if you like by using some finely chopped walnuts or pecan nuts in place of the bananas.