Pound meat to tenderize, then cut into VERY thin strips. Place flour and salt in plastic baggie. Add meat and shake to coat.
Melt butter in large skillet or frying pan. Add onion and mushrooms and sauté until onions are transparent. Add meat and all of the flour that is left in the bag.
Cook meat until brown. Add the soup and milk, stir and cover.
Simmer and stir occasionally, for about 2 hours or until meat is tender.
Crock Pot Instructions: If you don’t want to watch it that close you could put in a crock pot for 2 or 3 hours to simmer and tenderize. (This is a tougher cut of meat and takes a long time to tenderize.)
The sauce will thicken while cooking. If it becomes too thick you can add more milk or beef broth.
Add sour cream and Worcestershire sauce just before serving.