Preheat oven to 350°
Cut ham and turkey into large chunks.
Spray a casserole dish with non-stick cooking spray.
Lay the ham and turkey into the casserole dish and set aside.
Melt butter in a saucepan.
Stir in flour to make a roux and cook for 1-2 minutes stirring continuously.
Add the milk and continue to stir.
When the milk is hot add salt, pepper, garlic powder, onion powder, and nutmeg.
Add the cheese 1/4 cup at a time and continue to stir.
Pour the cheese sauce over the ham and turkey.
In a small bowl, mix butter, panko bread crumbs, and gruyere cheese.
Sprinkle the panko mixture over the top of the casserole.
Bake for 30 minutes.
Turn the oven up to broil and broil for 5 minutes until the panko begins to turn brown.