"Saute shrimp and onion in margarine for 10 minutes or until shrimp are tender. (Watch carefully as shrimp cook quickly and overcooking is about the only way to go wrong in preparing a shrimp dish. As soon as they turn pink, they are ready.) Add mushrooms and cook for 5 minutes more. Sprinkle in flour, salt, and pepper. Stir in sour cream and cook gently for 10 minutes, NOT allowing mixture to boil. Serve over rice. Makes 4-6 servings. "