1 1/2 pounds Certified Angus Beef ground chuck2 portabella mushrooms 1/2 cup Worcestershire Sauce 1/2 cup mayonnaise 2 tablespoons Dijon mustard 2 tablespoons chopped parsley 4 slices cheddar cheese 8 slices bacon, cooked 1/2 red onion, sliced 4 hamburger buns Salt and freshly ground black pepper to taste. Marinate mushrooms for 30 minutes in Worcestershire sauce (reserving 1 tablespoon) Combine mayonnaise, remaining Worcestershire, mustard, parsley and 1/2 teaspoon pepper. Remove mushrooms from marinade (discard unused marinade) and grill; slice mushrooms. Form ground chuck into 4 patties. Season with salt and pepper and grill Just before desired doneness is reached (recommended 160 internal temperature), top burgers with cheese and grill until cheese melts. Generously spread bun with flavored mayonnaise, top with burgers, red onion, mushrooms and bacon.