Preheat oven to 325 degrees. Cut butter into small pieces. In a food processor, mix butter and flour to a crumble. Add egg yolks, vanilla, salt, baking powder and sugar.
Mix until ingredients are just blended. Shape dough into a cylinder 1 1/2 inch diameter. Roll in coconut or nuts.
Chill until dough is firm. Slice into 1/4 inch thick slices and bake for about 18 minutes or until golden brown.
18 minutes 
