combine butter, flour, baking powder, salt in food processor. beat egg yolks and pour half into the flour mixture. add water slowly into flour until it becomes a semifirm mass. Shape dough into 2 balls, wrap and refrigerate for 15 minutes. in skillet, saute meat and onion in olive oil until meat is done. add remaining ingredients and saute for 1 minute more. Roll out dough to 1/8 inch thick sheet. then cut out circles with a 4-5 inch diameter. place 1 tablespoon of meat mixture into center of dough round. moisten the exposed edge with tap water and fold in half crimping the edges together. brush the top of the uncooked empanada with the remaining egg wash. place on baking sheet in 375 degree oven for 20 minutes until golden brown.