01 -
Roll beef into big 1/3 pound balls and keep them cold in the fridge for half an hour.
02 -
Run onions through a mandoline, press out the liquid, then refrigerate.
03 -
Fry bacon till crunchy, chop it into bits, and set aside.
04 -
Whisk mayo, mustard, ketchup, chopped bacon, Worcestershire, apple cider vinegar, spice rub, and red pepper flakes. Chill it until needed.
05 -
Heat your griddle, pour oil, then place beef balls down. Add onion slices on top and flatten. Sprinkle seasoning, then cook for 3 to 4 minutes.
06 -
Drizzle mustard on one side, flip the burgers, toss cheese on top, and cook until gooey—around 3 minutes.
07 -
Toast buns, smear some sauce, stack two patties on each bun, add extra sauce, then finish with the top bun.