Preheat oven to 350 degrees F and prepare a medium-large casserole dish with nonstick cooking spray.
In a large pot, cook shells as instructed on packaging. Drain and set aside to cool.
Over med-high heat, sauté ground turkey in a large skillet.
Once browned, turn down heat to medium heat and add frozen spinach, ½ cup mozzarella cheese, parmesan cheese, cottage cheese and egg to the turkey.
Season with garlic powder, onion powder, fennel seed, salt and pepper. Cook for 5-7, or until liquid has reduced. Set aside to cool.
Next pour the marinara into the casserole dish and spread evenly.
Once cooled, distribute the turkey-cheese mixture among the pasta shells.
Line the casserole dish with stuffed shells, making sure to nestle them into the sauce.
Sprinkle the tops with the remaining ½ cup of mozzarella cheese and bake for 15 minutes, or until cheese and marinara are bubbly. Enjoy warm.