Last year a friend made this for Russell's birthday in March. It would make a great April Fool's day for the family or work mates. The sponge used for Russell's cake was about 9 inches round and about 2 inces high. You could buy and use a square one if it was easier to get. The sponge can be washed an reused often ;-) Note that the sponge couldn't be included in the ingredients.