Add the sliced bacon to a dutch oven or large skillet over medium heat and cook, stirring, until the bacon is crisp. Use a slotted spoon to transfer the bacon to a paper towel lined plate.
Drain off all but about 2 tablespoons of the bacon fat and return the pan to the burner over medium heat. Add the chopped onions, sprinkle with kosher salt, and stir to coat.
Fry the onions in the bacon fat, stirring constantly, for about 3 minutes, or until the onions are crisp tender and fragrant.
Add the ground beef to the pan over the onions, pressing it out with a spoon so that you have a patty of beef. Let the beef cook, undisturbed, for 4 minutes before beginning to break it up with a spoon or a "chop and stir".
Continue cooking and stirring the beef until it is well-browned. Drain off any excess fat and return the beef to the pan over medium heat.
Whisk together the beef broth and cornstarch until smooth, then whisk in the ketchup, mustard, pickle juice, Worcestershire sauce, and black pepper. Pour over the beef, stirring well. Raise the heat to medium high and bring the sauce to a boil, then drop the heat to medium low and simmer for 2 minutes, or until thickened.
Remove from the heat. Stir the cheese into the pan and continue stirring gently until the cheese is fully melted and incorporated into the sauce. Stir in 2/3 of the crispy bacon, reserving 1/3 for garnish.
Serve over toasted rolls with reserved bacon, lettuce, tomato, slices of onion, and pickles if desired!