In a large mixing bowl, combine the ground turkey, grated Parmesan, breadcrumbs, chopped fresh basil, minced garlic, beaten egg, salt, and pepper. Mix gently but thoroughly until evenly incorporated. Avoid overmixing.
Shape the mixture into approximately 16 small meatballs (about 1 inch diameter). Heat a skillet over medium heat with a drizzle of olive oil. Cook meatballs in batches, turning occasionally, until browned on all sides and cooked through, about 10-12 minutes. Alternatively, bake on a greased baking sheet at 375°F (190°C) for 15-20 minutes.
Pour the marinara sauce into a medium saucepan and heat over low-medium heat. Add cooked meatballs and simmer gently for 5-7 minutes to marry flavors.
Preheat oven’s broiler. Slice hoagie rolls lengthwise, not all the way through. Spread about 1 tablespoon of pesto sauce inside each roll.
Use a slotted spoon to place 4-5 meatballs with marinara sauce inside each pesto-spread hoagie roll. Top with shredded mozzarella cheese.
Place assembled subs on a baking sheet and broil for 2-3 minutes until cheese is melted and bubbly. Watch closely to avoid burning.
If using, sprinkle cooked and crumbled turkey bacon over melted cheese for a smoky crunch.
Serve immediately with your favorite side like salad, roasted vegetables, soup, or chips.