Dredge beef in flour. Melt butter in a saucepan. Stir-fry until browned. Add onions and button mushrooms. Mix well. Pour beef stock. Cover and let boil. Reduce heat to low and cook covered until beef is tender. Add tomato paste and sour cream. Season with salt, pepper and Worcestershire sauce. Mix well and simmer over low heat for another 3 minutes. Lastly, stir in grated cheese. Serve warm with buttered pasta or plain rice.

Makes 10 to 12 servings.*Should you opt to use Monterey Beef tenderloin, sliced stroganoff style, stir fry until color changes and reduce water to 1 cup, since this will not entail a longer time to cook.