Combine beef, pork, and onion in a large skillet; cook until meat is browned, stirring to crumble. Drain well on paper towels. Combine meat mixture, parsley, salt, and pepper, mixing well.
Thaw pastry according to package directions. Cut pastry into 3 1/2-inch circles. Place about 1 tablespoon meat mixture on each pastry circle. Moisten edges of pastry with water; fold in half, making sure edges are even. Using a fork dipped in flour, press edges of pastry together to seal.
Place on baking sheet and bake at 375° for 20 minutes or until pastry is golden brown. Brush with melted butter.