Prep for baking. Heat oven to 400°F and arrange a rack in the upper third. Line a baking sheet with parchment paper.
Make filling. Combine ham, mozzarella, cheddar, apples, onion powder, chili powder, salt and pepper in a large bowl.
Prep egg wash. Beat the egg with the tablespoon of milk.
Roll out wrapper. Spread a small amount of flour on a clean work surface and lay an empanada wrapper on the flour, dusting lightly to coat. You want just enough flour that the dough won't stick to the counter but not too much that it coats the wrapper. It is better to use less and add a little bit more if needed. Roll the wrapper a few times with a rolling pin to make a slightly larger circle.
Fill empanada. Place 3 tablespoons of the filling in the middle of the circle and spread evenly in a horizontal line so when you fold the empanada over the filling fills the entire empanada and doesn't leave a doughy edge. Brush the egg wash around the edge of the wrapper.
Fold and seal. Fold empanada over to cover the filling so that both edges line up. Press the top dough around the filling. Use the tines of a fork to crimp the edges together. If the fork starts to get stuck in the dough, dip it in a little flour.
Repeat. Place the empanada on the baking sheet and repeat with remaining wrappers and filling.
Decorate. Brush the tops with the egg wash. Press a rosemary sprig on top of each empanada. Combine the white and black sesame seeds. Sprinkle seeds over the empanadas.
Bake empanadas. Bake in the top of the oven until flaky and golden brown, about 20-30 minutes.
Serve. Let cool 5 minutes and then serve warm with Mango Habanero Salsa.