In a frying pan over medium-high heat, add bacon. Cook until crispy and remove to paper towel covered plate. Reserve bacon grease in pan.
Reduce heat in frying pan to medium and add butter, garlic, and onions. Saute for 3 minutes then add mushrooms and Worcestershire. Cook for 3 minutes, then reduce heat to medium-low and let cook down will preparing burgers, stirring occasionally.
In a bowl, combine ingredients for burgers. Form into 4-inch patties and cook on a hot grill or grill pan for 7 minutes on each side. Remove from grill and place slice of cheese on top.
In a small bowl, combine mayo mixture ingredients.
Build the Burger: Spread mayo mixture onto top and bottom bun. Place a slice of lettuce then 2 slices of bacon on bottom bun. Then top with cheeseburger. Ladle mushrooms over bacon and then place top bun on.