Hollow out a long rectangular shape in the hoagie buns using a serrated knife, being careful not to cut all the way through the buns. Remove the excess bread and discard or save for homemade breadcrumbs or croutons.
4 hoagie buns,
Brush interior of rolls with garlic butter. Place rolls in casserole dish or on sheet pan and bake for 5 minutes.
Remove rolls from oven and line each bread cavity with a piece of provolone cheese. Add four meatballs and desired amount of sauce on top of cheese in toasted bread cavity. Sprinkle 2 tablespoons mozzarella cheese over each sandwich. Bake for another 5 minutes or until cheese is melted.
4 slices provolone cheese, ½ cup shredded mozzarella cheese
Remove from oven and sprinkle each sub with ½ tablespoon Parmesan cheese. Serve immediately with any remaining sauce.
2 tablespoons grated Parmesan cheese
Use uncut hoagie rolls from the grocery store bakery. They are usually a bit firmer and will hold their shape better when cooked.
You can either discard the parts of the rolls you hollow out of the buns or reserve them to make homemade breadcrumbs or croutons.
Serve any leftover marinara sauce from the meatballs on the side for dipping.
Feel free to swap in your favorite homemade meatball recipe for the frozen meatballs in these sandwiches.
We use three different types of cheese in these subs (provolone, mozzarella and Parmesan), but feel free to use only one or two if that's what you have on hand.
Short on time? Use the slow cooker to simmer the meatballs and sauce all day. All that's left to do when you get home is toast the buns and heat the sandwiches.