1 med. onion, chopped
1 tbsp. butter
1 lb. ground chuck
1 tsp. Worcestershire sauce
1/4 c. water
2 tbsp. cornstarch
1/2 tsp. instant beef bouillon
4 1/2 oz. sliced mushrooms, undrained

Shape beef into 8 thin patties. Saute onion in butter and spoon onions onto center of 4 patties. Sprinkle each with Worcestershire sauce. Cover with remaining patties; press edges to seal.

In same skillet, cook patties over medium heat until brown on one side. Carefully turn patties and cook until done.

Meanwhile, in small saucepan, combine cornstarch, water, bouillon, and mushrooms. Heat until thick, stirring often. Serve over burgers.