To make the jam: Heat a large sauté pan (that has a cover) over medium-high heat. Add the bacon and cook, stirring occasionally until browned but not crispy, about 8 minutes. Remove the bacon from the pan with a slotted spoon and let it drain on a paper towel-lined plate. Drain off all but 2-3 tablespoons of the bacon grease and then stir in the onions, about 1/4 tsp salt, and a pinch of pepper. Cover the pan to cook the onions for 2 minutes. Uncover the pan and in a splash of water, scraping the bits off of the bottom of the pan with a spatula or wooden spoon. Recover the pan and cook the onions for 10 minutes, stirring occasionally, until the onions are soft and lightly browned.

After the onions have cooked for 10 minutes, stir in the balsamic vinegar, mustard, and water then return the bacon to the pan and bring the mixture to a simmer. Simmer uncovered until the sauce thickens and is almost completely absorbed, about 2-4 minutes. At this point, the jam can be covered and refrigerated (you can make it up to 2 days in advance). If using immediately, set it aside in a bowl until ready to use.

To make the burgers: Using a fork, lightly mix the finely diced bacon with the ground beef, Worcestershire sauce, salt, and ground pepper in a medium bowl until the ingredients form a uniform mixture. Shape the burger mixture into four equal-sized patties, about 1-inch thick. Cook the burgers on a grill pre-heated to medium-high, about 4-5 minutes per side. Once you flip the burgers, add the cheese (if the cheese is thinly sliced, give it a minute or two on the second side before adding it). Once cooked to desired doneness, remove the burgers from the grill and set them aside to rest for 5 minutes before adding any toppings, place on the buns, serve and enjoy!