Make the meatball mixture

• In a bowl, combine the ground beef, breadcrumbs, egg, parmesan, garlic and parsley.
• Season with salt and black pepper and mix until just combined.
• Roll into evenly sized meatballs.

Brown the meatballs

• Heat the olive oil in a frying pan over medium heat.
• Sear the meatballs on all sides until browned.

Simmer in tomato sauce

• Pour the tomato sauce over the meatballs.
• Simmer gently until the meatballs are cooked through and the sauce thickens.

Assemble the subs

• Fill the split sub rolls with the meatballs and sauce.
• Top generously with shredded mozzarella.

Bake and serve

• Bake the subs until the cheese is melted and the bread is toasted.
• Serve hot.