Add onion, soup and seasonings. Simmer 1 1/2 to 2 hours or until meat is tender. A cup of water may be added if necessary, and you may need to add additional water to prevent sauce from scorching.
Add mushrooms and sour cream and heat until just hot. Do not cook after sour cream is added or it will curdle.
Serve with cooked noodles (6-ounce package) or rice ring. Makes 6 servings.