Preheat the oven at 180°c.Cream the butter and sugar together, add the vanilla and cocoa and mix well. Add the sifted flour, baking powder and mix through using your hands to form a soft dough.Pinch off small pieces of dough and roll them into tiny balls.Place the balls of dough on greased oven trays or lined with baking paper, spacing the dough balls apart.Bake for 15mins and leave them to cool.