Coat beef strips by shaking in a clean plastic bag with flour. Alternatively, dredge each piece in a shallow pan filled with flour.
In a small bowl, combine soup, mushrooms (including liquid), tomato paste and Worcestershire sauce; set aside.
Heat a large skillet over medium-high heat. Add oil and quickly brown meat. Stir in onion. Add reserved sauce to meat and simmer, covered, until meat is tender, about 1 to 1 1/2 hours. Add sour cream to sauce just before serving, stirring thoroughly to combine. Heat thoroughly, but do not boil.
While meat is cooking, prepare noodles according to package directions. Drain and serve with stroganoff.Servings: 8