Start by preheating your oven to 375 F.
Cream the butter and sugar until it is light and fluffy.
Add the egg and mix well
In a separate bowl, combine the flour and baking powder
Alternately add the flour-mixture and milk, mixing between each addition.
Gently fold in the berries.
Pour the batter in a greased 9 x 13 in pan and set aside while you prepare the topping.