1 1/2 pounds Certified Angus Beef ground chuck2 portabella mushrooms1/2 cup Worcestershire Sauce1/2 cup mayonnaise2 tablespoons Dijon mustard2 tablespoons chopped parsley4 slices cheddar cheese8 slices bacon, cooked1/2 red onion, sliced4 hamburger bunsSalt 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.