Preheat your oven: Set your oven to 375°F (190°C) to ensure it's hot and ready for baking your delicious subs.
Cook the spaghetti: Boil a pot of salted water and add 8 oz of spaghetti. Cook according to the package instructions until al dente, then drain and set aside.
Prepare the ground turkey/chicken: In a skillet over medium heat, brown 1/2 lb of ground turkey or chicken until fully cooked, stirring occasionally. Season it with salt and pepper, and drain any excess fat.
Add marinara sauce: Pour in 24 oz of marinara sauce into the skillet with the cooked meat. Stir in 1 tsp of Italian seasoning and let it simmer for about 5 minutes, allowing the flavors to meld. Then, mix the drained spaghetti and 1/2 cup of grated Parmesan into the sauce until evenly coated.
Prepare the hoagie rolls: While the filling simmers, carefully hollow out the inside of 2 large hoagie rolls or French bread loaves to create 'boats' for your spaghetti filling. Be careful not to cut through the bread entirely.
Make the garlic butter: In a small bowl, combine 1/4 cup of melted butter with 3 minced cloves of garlic, 1 tsp of dried parsley, and 1/2 tsp of garlic powder. Mix well.
Brush the bread: Generously brush the garlic butter mixture onto the inside and outside of your hollowed-out bread loaves, ensuring they are well coated.
Fill the bread boats: Spoon the cheesy spaghetti filling into each hoagie roll, packing it lightly. Top the filled subs with 1 cup of shredded mozzarella.
Bake the subs: Place the stuffed bread on a baking sheet and bake for 10-12 minutes or until the bread is crispy and the cheese is bubbly and golden brown.
Garnish and serve: Remove the subs from the oven, sprinkle with fresh parsley, and serve immediately. Enjoy the delicious medley of flavors!