Step 1: Make the Meatballs

1. Prepare the Mixture: In a large mixing bowl, combine the ground beef, ground pork (if using), breadcrumbs, Parmesan cheese, egg, garlic, parsley, Italian seasoning, salt, pepper, and milk. Mix gently with your hands or a spoon until just combined; do not overmix.
2. Form the Meatballs: Roll the mixture into golf ball-sized meatballs (about 1 ½ inches in diameter) and place them on a baking sheet lined with parchment paper.
3. Brown the Meatballs: Heat a large skillet over medium heat with a drizzle of olive oil. Brown the meatballs on all sides, about 2-3 minutes per side. They don’t need to cook through completely; they’ll finish in the sauce.

Step 2: Make the Marinara Sauce

1. Sauté Aromatics: In the same skillet, heat 2 tbsp olive oil over medium heat. Add the chopped onion and sauté until translucent, about 3-4 minutes. Add garlic and cook for an additional minute.
2. Add Tomatoes and Seasoning: Stir in the crushed tomatoes, sugar (if using), basil, oregano, red pepper flakes, salt, and black pepper. Bring to a simmer.
3. Simmer with Meatballs: Gently add the browned meatballs to the sauce, cover, and simmer for 20-25 minutes, stirring occasionally. The meatballs should be fully cooked and infused with the sauce’s flavor.

Step 3: Prepare the Bread

1. Preheat the Oven: Set your oven to broil or 400°F (200°C) if you prefer baking.
2. Make Garlic Butter: In a small bowl, mix softened butter with garlic powder. Spread the mixture over the cut sides of the hoagie rolls.
3. Toast the Bread: Place the rolls on a baking sheet, buttered side up, and toast in the oven for 2-3 minutes or until lightly golden.

Step 4: Assemble the Subs

1. Fill with Meatballs: Place 3-4 meatballs (depending on the roll size) onto each toasted hoagie roll. Spoon extra marinara sauce over the meatballs.
2. Add Cheese: Top each sub with shredded mozzarella or slices of provolone.
3. Melt the Cheese: Return the assembled subs to the oven and broil for 1-2 minutes, just until the cheese is melted and bubbly.

Step 5: Serve and Enjoy

1. Finish with Parmesan: Sprinkle grated Parmesan and chopped parsley on top for added flavor.
2. Serve Hot: Serve the subs immediately with your favorite sides, such as a crisp salad, fries, or chips.