Brown steak cubes over low heat.
Add the mushrooms and soup mix, bring to a boil and then turn down to simmer.
Simmer covered until the beef is tender (about 40 minutes) stirring occasionally.
Simmer uncovered until broth reaches desired consistency.
Add the sour cream, mix well, and heat through (about 5 minutes).
Serve over either mashed potatoes or buttered noodles.