In a medium bowl mix together ground beef, onion soup mix, egg, bread crumbs, and garlic. Shape mixture into 6 patties.
In a skillet brown patties over medium heat, just until juices run clear. Remove to plate.
Saute mushrooms in pan. After they are browned add beef stock, Heinz 57, and Worcestershire. Stirring often, simmer until slightly thickened. Remove from heat and stir in sour cream. Add patties back into pan to reheat in sauce. Serve over mashed potatoes or egg noodles.