Sift together the flour, baking powder, and salt, then add the butter, eggs, and milk. Knead dough until it forms a solid ball. Wrap it in plastic wrap and let it rest for 15 minutes.
Coat the edge of half a circle with the egg wash, fill the circle with about 1 ½ tablespoons of the filling, fold it in half and pinch the edges shut. When you are all done filling them, seal them completely by using the tips of a small fork to press the edges shut. Brush them with the egg wash before baking.
Bake as many as eight at a time on a parchment-lined large baking sheet for 15-17 minutes. Once they're done baking, remove them from the baking sheet and let them cool off on a cooling rack. Serve with any salsa or leftover cranberry sauce if you have some.
If you can't make the empanadas right away, it's okay. You can also refrigerate the dough overnight. When you are ready to use it, bring it out of the fridge and let it rest 10-15 minutes before rolling it out.