Mix Ingredients: In a large mixing bowl, combine ground meat, breadcrumbs, Parmesan cheese, beaten egg, minced garlic, parsley, oregano, salt, and pepper. If using milk, add it now. Mix until just combined. Avoid overmixing as this can make the meatballs tough.
Shape Meatballs: Using your hands or a scoop, form mixture into meatballs, around 1 to 1.5 inches in diameter.
Preheat Air Fryer: Set your air fryer to 400°F (200°C) and allow it to preheat for a few minutes.
Arrange in Air Fryer: Place meatballs in the air fryer basket in a single layer, ensuring they are not touching to allow for proper air circulation.
Cook: Air fry the meatballs for approximately 10-12 minutes, flipping them halfway through the cooking process. Ensure they are cooked through and have an internal temperature of 165°F (74°C).
Split your sub rolls without cutting them all the way through.
Fill each roll with an appropriate number of meatballs (usually 3-4 depending on size).
Spoon marinara sauce over each meatball.
Sprinkle generously with mozzarella and, if desired, Parmesan cheese.
Lightly spray the outside of the sub rolls with olive oil or cooking spray for a crispy finish.
Carefully place the assembled subs into the air fryer basket.
Lower the temperature to 360°F (182°C).
Cook for 3-5 minutes or until the bread is toasted to your liking and the cheese is melted and bubbly.
If desired, sprinkle with fresh chopped basil or parsley for an aromatic finish.
Serve your meatball subs hot with a side of marinara for dipping, a crisp salad, or your favorite chips.