A hearty handheld empanada makes for a delicious appetizer or on-the-go meal. Pretty much anything wrapped in a flaky, chewy, buttery puff pastry dough is bound to be delicious. All the better when that filling is a melange of sweet tomatoes and onions, satiating potatoes, and flavorful ground beef, all carried by melted fresh mozzarella and Parmigiano-Reggiano. Paired with rice, beans, and a shaved cabbage salad or slaw, this appetizer can become the main dish of a full meal.