Cook the Bacon: Heat a skillet over medium heat. Add 4 slices of bacon, frying until crispy, about 5-7 minutes. Remove and drain on paper towels, leaving the fat in the skillet.

Caramelize the Onions: In the bacon grease, add the sliced onion. Cook over medium-low heat for 10-15 minutes until soft and golden. Pour in the stout and simmer until reduced by half; season with salt and pepper.

Prepare the Beef Patties: In a bowl, combine ground beef, Worcestershire sauce, salt, and pepper. Mix gently, then form into 4 patties larger than the buns.

Cook the Patties: Heat the skillet over medium-high or prepare a grill. Cook patties for 3-4 minutes on each side until brown. Add cheese on top to melt during the last minute.

Make the Sauce: Combine sour cream and Dijon mustard in a small bowl. Set aside.

Toast the Buns: Melt butter in a skillet. Split burger buns and toast cut-side down for 2-3 minutes until golden brown.

Assemble the Burgers: Start with the bottom bun, layer with a beef patty, caramelized onions, and bacon. Drizzle with sauce and top with the other bun.

Serve and Enjoy: Serve hot alongside crispy fries or slaw, and enjoy the flavors of this comforting pub favorite!