Put 16 patty cups into a muffin tray/s. Preheat oven to 190 degrees C.
Cream the butter and the sugar together until pale and fluffy. Gradually beat in the eggs, a little at a time, beating well after each addition. Fold in the flour.
Half fill the patty cups. Bake in preheated oven for 15-20 minutes, until golden brown. Transfer to a wire rack to cool.
To make the icing, sift the icing sugar into a bowl. Add a few drops of vanilla if desired.
Using a wooden spoon, gradually stir in the hot water until the mixture is the consistency of thick cream. Beat until white and smooth and the icing is thick enough to coat on the back of the spoon. Add colouring if you want and use immediately.
Ice the cooled cakes and add extra decorations like hundreds and thousands, if you like.
If the mixture curdles when adding the eggs tip all the beaten eggs in and quickly stir in the flour.