Preheat oven 400 F. Grease or spray 13 x 9 inch baking pan. Chop the bread until fine crumbs form (abt. 1 cup). Grate onion for 1 tbs. In large bowl, mix bread crumbs and grated onion with ground turkey, spinach, salt, pepper, and egg. Shape turkey mixture into 16 meatballs. Place meatballs in pan and bake 25 minutes or until meatballs are lightly browned and cooked through. Meanwhile, thinly slice carrots and cut mushrooms into 1/2" pcs. In 3 quart saucepan over high heat, heat carrots, mushrooms, pasta sauce, and 1/2 cup water to boiling. Reduce heat to low; cover and simmer 20 minutes. When meatballs are done, add to sauce; cover and simmer 10 minutes longer to blend flavors and cook vegetables until tender. Serve over spaghetti or rice. Nutritional information per serving (without spaghetti or rice): Calories 435, Fat 20g, Cholesterol 112mg, Sodium 1595mg.