While fully cooked empanadas can be made head and reheated in the oven to crisp them up, I prefer making the empanada filling ahead, and either storing the filling in the fridge overnight and filling just before cooking, or filling them and the uncooked empanadas well-wrapped with plastic in the refrigerator overnight. When you're ready to make them, brush with egg wash just before baking or place them directly into the hot oil to fry.