Preheat oven to moderate, 180c. Line a 12 hole muffin pan with paper patty pans.
In a bowl, using an electric mixer beat the butter, sugar and vanilla together until light and fluffy. Add eggs one at a time, beating well after each addition.
Fold flour into creamed mixture alternately with milk until just combined, and then fold in berries. Spoon into cases until 2/3 full.
Bake for 15-20 minutes, until cooked when tested, they will spring back with a gentle touch. Transfer to a wire rack to cool.
Icing, Sift icing sugar into a bowl and add the butter. Pour boiling water onto the butter, and stir to combine. Spread over the cakes and leave to set.