Preheat oven to 175 degrees C (350 degrees F). Grease cookie tins.
In a large bowl, cream together the butter and sugar until smooth. Mix in the egg and vanilla. Combine the flour and baking powder; stir into the creamed mixture until blended. Divide dough into walnut sized portions. Roll each piece into a rope and then shape into a loop. Place cookies 5cm apart on the prepared cookie tins.
Bake for 8 to 10 minutes in the preheated oven, until firm and golden at the edges.