Preheat oven to 400°F. Add the meatballs to the skillet.
Cover the meatballs with pasta sauce.
Top with most of the Parmesan cheese, then the mozzarella cheese, reserving a bit to sprinkle on the individual sandwiches.
If using, add freshly chopped basil.
Bake for 15 minutes uncovered or until the meatballs are heated through and the cheese has melted.
Slice the bread open, and place the meatballs and melty cheese.
Sprinkle a bit more of the remaining freshly grated cheeses and some fresh basil.
Place them on a cast iron baking tray and pop them under the broiler for a couple of minutes to melt the new top layer of cheese and toast the sub rolls.
VariationsBread — hoagie rolls, French bread, even hot dog buns will workMeatballs — pre-cooked frozen meatballs, meatball recipes made from different meats (ground meat such as ground turkey, ground pork, or Italian sausage.)Extra flavor — freshly ground black pepper, red pepper flakes, fresh herbs like fresh parsley or oregano, or spread garlic butter inside the sub rolls before adding the warm meatballs and cheese.What do serve with meatball subs