Preheat oven to 350F. Lightly grease 13 x 9-inch baking pan; set aside. Brown ground beef in medium skillet over medium-high heat. Add onion and garlic. Sauté 3 to 4 minutes until onion is tender. Drain off excess fat. Remove from heat and add spinach, cottage cheese, eggs, salt and pepper. Stir until well mixed. Fill each shell with 1/4 cup meat mixture. Place filled shells in prepared baking pan. Pour spaghetti sauce evenly over filled shells. Sprinkle Parmesan, then mozzarella cheese over Sauce. Bake 30 minutes.