Rub a large, heavy pan with the salt pork. Place it in the pan with the oxtail, salt, pepper, thyme, bay leaf, parsley sprig, and water; bring to a boil. Lower heat; partially cover and simmer slowly for 4 hours. Strain the broth and remove the meat from the oxtail joints; discard the bones. Return the meat to the strained broth and add the barley or rice. Cover and cook over low heat for 30 minutes. Add the carrot, leek, onion, celery, potato, and bacon and simmer covered for 30 minutes more. Taste for seasoning and add Madeira. Garnish each serving with parsley.

Editors Note: Oxtails make very flavorful soup because of the gelatinous matter they contain. But it may be difficult to find oxtails at a regular supermarket meat department. You may need to deal with a local butcher or slaughterhouse.