2In a bowl, combine chopped bacon, mayonnaise, Worcestershire sauce, maple syrup, ketchup, and yellow mustard. Mix until well combined to make the bacon jam.
3Slice the onion and cook on a griddle or skillet over medium heat until caramelized.
4Form the ground beef into two burger patties.
5Sear the burger patties on the griddle or skillet until cooked through and nicely charred on both sides.
6Butter one side of each bread slice.
7Place a slice of bread, buttered side down, on the griddle. Top with a slice of cheese, a burger patty, caramelized onions, a generous spoonful of bacon jam, another slice of cheese, and another slice of bread, buttered side up.
8Cook the sandwich on both sides until the bread is golden and crisp and the cheese is melted.
9Repeat for the second sandwich. Slice and serve hot.