Preheat oven to 400 degrees F. In a big pot boil 6 cups of water and cook shells al dente style (according to package), add salt taste.
While the shells are cooking, heat a large pan or skillet. Add the ground beef, onion and garlic (no oil needed) and cook for 3-4 minutes or until the beef is browned and the onion is softened. Add the spinach and spices and cook down spinach for 2 minutes. Stir in about half the marinara sauce.
After the shells are cooked (be careful not to overcook because they will start to break apart), arrange them on a 13x9 casserole dish or any oven safe pan. Fill each shell with about 2-3 tablespoons of the meat mixture then pour the marinare over the shells. Sprinkle with mozzarella and Parmesan cheese, cover with foil and cook for 15 minutes. Remove foil and broil for a minute or two to brown the cheese if desired.