Preheat over to 180°C/Gas 4.
Line 8 ANTA small mugs with muffin cases.
Cream the butter and sugar together until light and fluffy.
Add the eggs one at a time until fully combined and mix through the vanilla extract.
Slowly sift in the flour (and cocoa if making chocolate) and fold through the mixture.
Carefully spoon into the mugs and bake for 8-10 minutes until springy to the touch.
Once they are cool, remove them from the mugs.
Mix the icing sugar and water together in a bowl.
Dip the cupcakes in the icing.
