Step 1: Make the Meatballs

1. In a mixing bowl, combine ground beef, breadcrumbs, Parmesan, egg, garlic, Italian seasoning, salt, pepper, and red pepper flakes.
2. Add milk and mix until just combined. Do not overmix.
3. Roll into 1-inch meatballs and place on a plate.

Step 2: Cook the Meatballs

1. Heat olive oil in a large skillet over medium heat.
2. Add meatballs and cook for 8-10 minutes, turning occasionally, until browned and fully cooked.
3. Remove from the skillet and set aside.

Step 3: Simmer the Marinara Sauce

1. In the same skillet, heat olive oil over medium heat.
2. Add marinara sauce, garlic powder, and oregano. Simmer for 5 minutes.
3. Return the meatballs to the sauce and coat well. Let simmer for another 5 minutes.

Step 4: Prepare the Hoagie Rolls

1. Preheat oven to 375°F (190°C).
2. Slice the hoagie rolls lengthwise, leaving one side attached.
3. Mix melted butter with garlic powder and brush onto the inside of each roll.
4. Toast in the oven for 5 minutes, until golden and crispy.

Step 5: Assemble the Meatball Subs

1. Place 3-4 meatballs inside each toasted hoagie roll.
2. Spoon extra marinara sauce over the meatballs.
3. Lay a slice of provolone cheese over the top.
4. Bake for 5 minutes, or until the cheese melts and is bubbly.

Step 6: Garnish & Serve

1. Sprinkle with fresh basil or parsley.
2. Serve hot with a side of cheese spaghetti, fries, or a salad.