Preheat the oven to 375 degrees. Set a wire rack inside a rimmed baking sheet lined with foil. Place the bacon slices on a plate.
In a small bowl, mix together the brown sugar with three tablespoons of maple syrup. Press the brown sugar mixture onto one side of the bacon.
Transfer the bacon to the wire rack, brown sugar side up. Bake it until it is crispy (about 30-40 minutes).
In a medium bowl, use your hands to combine the beef, pork, Worcestershire sauce and seasonings. Gently shape the beef mixture into six patties that are about four inches in diameter.
In a skillet, heat the oil over medium-high heat. Cook the patties, pressing them with the back of a spatula. Cook them for 8-10 minutes (or your desired doneness), turning them once.
During the last minute of cooking, top each patty with a slice of cheese. Transfer the patties to a plate, then fry the eggs over easy. Transfer the eggs to paper-towel lined plate.
In a small bowl, mix two tablespoons of maple syrup and the Dijon mustard. Spread the maple-mustard sauce on toasted brioche buns. Place the patties on the bottom halves of the buns. Top with spinach, bacon, a fried egg and top bun.