Coarsely chop the peanuts.
Cream the butter and sugar together in a bowl.
Add the egg and mix well.
Sift the flour and baking powder, then add to the mixture and combine.
Add the chopped peanuts and knead the dough.
Shape the dough into balls and place them on a pan.
Bake in a preheated oven at 180°C (356°F) for 15 minutes.