Preparation / Directions:
1. Cut the butter into 1/4 inch cubves.
2. Place the flour, baking powder, salt, and butter in a mixing bowl. Combine the ingredients with a pastry cutter (or with the steel blade in a food processor).
3. Beat the egg yolks. Mix half of them into the flour mixture. Reserve the remainder for step 12.
4. Incorporate the water slowly into the flour mixture until the dough becomes a cohesive and semifirm mass.
5. Shape the sough into two balls. Wrap them in plastic wrap and refrigerate them for 15 minutes.
6. Preheat the oven to 375 degrees F.
7. Heat the oil in a large saute pan or skillet over moderate heat. Saute the meat for 3 minutes, stirring frequently. Transfer the meat with a slotted spoon to a warm bowl.
8. Add the onions to the pan and saute them over low to moderate heat for 3 minutes, stirring frequently. (Add 1 or 2 extra teaspoons of oil if necessary).
9. Return the meat to the pan and add the remaining ingredients. Cook the mixture for 1 minute, stirring constantly. Reserve it for step 11.
10. Roll each ball of dough on a lightly floured board into a 1/8-inch thick sheet. Using a cookie cutter with a 4- to 5-inch diameter, cut out rounds. Collect the scraps and repeat step 10 until the dough is used up.
11. Place one tablespoon of the meat mixture in the center of each dough round. Lightly moisten the exposed dough with cold tap water. Fold each round in half, creating a half-moon shape. Crimp the two edges of dough together, so that the stuffing cannot ooze out during the baking step.
12. Brush the tops of the uncooked empanadas with the remaining egg yolk.
13. Place the uncooked empanadas on an ungreased baking sheet. Bake them in the middle of the oven until the tops become light golden brown (roughly 20 minutes). Serve the empanadas fresh from the oven.