Beef Stroganoff

1/4 cup shortening 1/2 cups fresh thinly sliced mushrooms 1 1/2 lbs. sirloin tip cut into 1/4 inch strips 2 tbsp. flour 3/4 lb. fresh tomatoes or 1 cup of canned tomatoes 1 1/2 tsp. salt 1/8 tsp. pepper 1/4 tsp. Worcestershire sauce 1/2 cup sour cream   Saute onions in shortening for about 10 minutes, add mushrooms, cover and continue cooking for 5 minutes. Remove onions and mushrooms and place in a bowl.   Brown meat slowly and thoroughly. Sprinkle with flour and stir until blended. Add tomatoes and seasonings. Cover and simmer very slowly for 1-hour stirring occasionally. …