Preheat the oven to 375F. Arrange bacon on a slotted broiler pan and bake until crisp, about 15 minutes.
In a large bowl, season the beef with salt and pepper. Mix in the Worcestershire, parsley and onion. Form 4 large patties (thinner in the middle for even cooking.)
In a large skillet or cast-iron griddle, heat the oil over medium-high heat. Add the patties and grill, turning once, for about 8 minutes for medium-rare. Transfer to a plate.
In the bowl of an electric mixer, combine the cheddar, pimientos, cream cheese, mayo, hot sauce, paprika and garlic until well mixed, 1-2 minutes.
Reheat the skillet or griddle over medium heat. Butter 1 side of each bread slice, placing buttered side down on a work surface. Spread each bread slice with some cheese mixture, top with a burger, 2 pieces of bacon and another bread slice. Griddle until golden and the cheese is melted.