Melt Becel® Buttery Taste margarine* in large skillet over medium-high heat and brown steak with mushrooms. Remove from skillet; keep warm.
Stir Knorr® Lipton Recipe® Onion Soup Mix with 25% less sodium, water and flour into same skillet.
Bring to boil over high heat, reduce heat to low and simmer, stirring constantly, until sauce is thickened. Continue simmering, stirring frequently, for an additional 4 minutes. Return steak and mushrooms to skillet.
Stir in sour cream and heat through. Serve over hot cooked noodles.