Prepare the Meatball Mixture: In a large mixing bowl, combine the ground turkey, beaten egg, minced garlic, ricotta cheese, breadcrumbs, grated Parmesan, chopped fresh basil, garlic powder, dried basil, and a generous pinch of salt and pepper. Gently mix everything with your hands or a spoon until just combined. Avoid overworking the mixture to keep the meatballs tender and juicy.
Brown the Meatballs: Heat the olive oil in an oven-safe skillet over medium heat. Shape the turkey mixture into evenly sized meatballs, about 1.5 inches in diameter. Add them carefully to the hot pan, making sure not to overcrowd. Cook for about 10 minutes, turning occasionally, until all sides are golden brown and seared. This step seals in the moisture and builds flavor.
Add Sauce and Cheese: Pour the marinara sauce evenly over the browned meatballs in the skillet. Scatter torn fresh mozzarella pieces on top of the meatballs. Transfer the skillet to the preheated oven and bake at 400°F (205°C) for 20 minutes, until the cheese is melted and bubbly, and the meatballs are fully cooked through.
Toast the Sub Rolls: While the meatballs bake, place the sub rolls on a baking sheet. Once the meatballs are done, scoop them along with the sauce and melted cheese into each roll. Return the filled sandwiches to the oven for 5 minutes to toast the bread until golden and slightly crispy.
Garnish and Serve: Remove the subs from the oven and sprinkle generously with extra fresh basil, Parmesan cheese, and a pinch of crushed red pepper flakes if you like a little heat. Serve immediately and enjoy the melty, flavorful sandwich experience!