01 -
Form the ground chuck into 1/3 pound balls and refrigerate for 30 minutes.
02 -
Slice the white onions as thin as possible using a mandoline. Squeeze out excess water and refrigerate.
03 -
Crisp up the bacon, chop it, and set it aside.
04 -
Mix mayonnaise, ketchup, mustard, bacon, Worcestershire sauce, apple cider vinegar, all-purpose rub, and red pepper flakes. Refrigerate until ready to use.
05 -
Heat a griddle to medium-high heat. Apply avocado oil and place burger balls on the griddle, 2-3 inches apart. Add sliced onions on top, smash them down with a burger press, and season with salt, pepper, and garlic.
06 -
Cook for 3-4 minutes, then spread mustard on top of patties, flip, and add pepper jack cheese. Cook until the cheese melts, about 3 more minutes.
07 -
Toast burger buns on the griddle. Spread Baconnaise sauce on the bottom bun, layer double smash burgers, add more Baconnaise sauce on top, and place the top bun to finish.