In a large saucepan, heat olive oil and gently brown garlic. Add onion, carrots and if using, the potato (this helps to thicken the soup as it breaks up), and after 1 minute, the broth. Add escarole, cover and let come to a boil. Lower to simmer for 1 hour. For more liquid soup, add a little more broth or water. Its also delicious to add spareribs and/or a few pieces of Italian sausages before you brown the vegetables. Make sure the meat is well cooked. Then add everything else. Serve sprinkled with grated cheese and soft Italian bread.