Position racks in the upper and lower thirds of the oven and preheat to 425˚. Line 2 baking sheets with foil and lightly coat one with cooking spray. Combine the ground chicken, breadcrumbs, ⅓ cup parmesan, the parsley, salt, oregano, pepper and egg in a large bowl. Mix well with your hands.
Form the meat into 24 small meatballs (about 2 tablespoons meat each) and arrange on the oiled baking sheet. Bake on the upper oven rack until cooked through, 15 to 18 minutes.
Meanwhile, mash the butter, garlic powder and remaining ¼ cup parmesan in a small bowl. Put the rolls on the second baking sheet and open but do not fully separate the halves. Evenly spread the insides with the butter.
Bake the rolls on the lower rack until lightly toasted, 8 to 10 minutes.
Evenly divide the meatballs between the rolls and top with the marinara sauce and mozzarella.
Bake the subs until the sauce is hot and the mozzarella is melted, 8 to 10 minutes. Sprinkle with basil and serve with chips.
