In a large mixing bowl, combine the ground beef, ground pork, breadcrumbs, Parmesan cheese, milk, egg, minced garlic, chopped parsley, salt, black pepper, oregano, and basil.
Mix the ingredients together using your hands or a spoon until well combined. Be careful not to overmix, as this can make the meatballs tough.
Roll the mixture into meatballs, about 1 1/2 inches in diameter, and place them on a baking sheet.
Cook the Meatballs:Preheat a skillet over medium heat and add a drizzle of olive oil. Add the meatballs to the skillet, making sure not to overcrowd them. Cook for about 8-10 minutes, turning occasionally, until they are browned on all sides.
Once browned, transfer the meatballs to a saucepan with the marinara sauce. Let them simmer in the sauce for 15 minutes, allowing the flavors to meld together.
Prepare the Rolls:Preheat your oven to 375°F (190°C). In a small bowl, mix the softened butter with the minced garlic. Spread this mixture on the inside of each hoagie roll.
Place the rolls on a baking sheet and bake for about 5 minutes, or until they are lightly toasted.
Assemble the Sandwiches:Once the rolls are toasted, remove them from the oven and spoon a generous amount of marinara sauce into each roll. Place 3-4 meatballs in each roll, then top with more marinara sauce.
Sprinkle shredded mozzarella cheese and grated Parmesan cheese over the meatballs.
Return the sandwiches to the oven and bake for another 5-7 minutes, or until the cheese is melted and bubbly.
Garnish with fresh basil or parsley, if desired, and serve immediately.