If you are doubling the cake recipe you will need to double this quantity as well. I like to do a crumb layer first - keep the cake in the fridge until the crumb layer has hardened and then do the decorative frosting.
Sift icing sugar, and the three spices into a bowl.
Beat the butter in a mixing bowl until softened. Add the sifted ingredients slowly until combined.
Add the milk a few drops at a time until the desired consistency is reached.
Any extra frosting can be kept in the deepfreeze.