In a large soup kettle or Dutch oven, cook onion, leeks and garlic in oil until tender, about 5 minutes Add chicken broth, potatoes, carrots, turnips and mushrooms. Cover and cook over low heat until vegetables are tender, about 30-40 minutes. Add spinach and sausage; cook for 10 minutes. Add pasta, salt and pepper; heat through. Serve with Parmesan cheese if desired. Yield: 16 servings (1 gallon).