Prep: 1. Preheat oven to 400 and grease a 9x13 baking dish. 2. Chop onion, parsley, garlic. 3. Grate cheese. Make: 1. In a large bowl, mix onion, parsley, egg, 3 tablespoons of the marinara sauce, garlic, salt, and pepper. 2. Add parmesan and bread crumbs (if using), and mix in the turkey. 3. Arrange peppers in the baking dish, then fill the halves with turkey mixture, dividing equally and mounding slightly. 4. Pour marinara sauce over the stuffed peppers. 5. Bake uncovered until peppers are tender and beginning to brown, about 45 minutes. Allow to cool slightly and serve.