Line the base and sides of a 20cm cake tin with baking paper. Preheat oven to 160°C.
Melt butter and allow to cool to room temperature. Once cooled, place in a bowl with all the remaining cake ingredients and mix with a whisk (it will be quite a runny mixture).
Pour batter into cake tin and bake for about 50 minutes, until a skewer inserted comes out clean. Allow cake to cool completely on a wire rack.
To make icing, combine cream cheese, icing sugar and coffee, whisking until smooth. Add a little more coffee as desired to suit your tastes. Spread over cooled cake. Dust with a little cocoa for decoration if you like!