In a 3-quart saucepan, saute the onion in margarine until it is soft but not brown. Add milk, potatoes, lox, wings of lox (if used) and pepper. Simmer until potatoes are very soft, about 30 minutes. Make sure the soup does not boil. Remove from heat and taste for seasoning. Remove wings of lox, pick away any cooked lox and place in soup, and discard the wings. Taste for seasoning. If the lox was not salty, the soup may need some salt.
*If you are buying your lox from a deli where they slice it fresh, ask to buy the wings, which are usually discarded. They are the large fins that are cut away to allow for easier slicing.
Advice from Mama: I'm against violence in cooking in general, but most soups and stews in particular should never be cooked at a violent boil. A gentle simmer is what's needed for the soup ingredients to develop a full flavor without losing their texture and integrity. Milk should never be boiled because it will foam up and boil over and make a mess and a smell you won't believe. Fish, too, should always be cooked on a gentle heat. So keep your heat low enough for the liquid to cook at the gentlest simmer.
Source: Mama Leah's Jewish Kitchen by Leah Loeb Fischer with Maria Polushkin Robbins
Yield: 6 servings