Preheat the oven to 400ºF. Place the bacon on a broiler pan or rack-lined baking sheet and bake until the fat is partially rendered, about 15 minutes. Baste the bacon with maple syrup; bake 5-6 minutes more.
Heat a cast-iron skillet over medium-high heat. In a bowl, combine the beef, Worcestershire and onion (grate the onion over the bowl so the juices fall into the meat). Stir in the mustard; season with salt and lots of pepper. Form into 4 patties (making them thinner at the center and thicker at the edges). Drizzle the patties with oil; cook, flipping once, until a nice crust forms, about 7 minutes. Top with the cheese and cook for about 2 minutes to melt.