Cook bacon until crispy. Drain and set aside. Reserve bacon fat.
In a small bowl, mix mayonnaise, adobo sauce, minced chipotle peppers, whiskey, brown sugar, and Worcestershire sauce. Set aside.
Divide ground beef into 4 equal portions. Gently form into loose balls.
Heat a cast-iron skillet or griddle over medium-high heat. Add a tablespoon of reserved bacon fat.
Place beef balls on the hot skillet. Immediately smash each ball flat with a sturdy spatula or burger press. Season generously with salt and pepper.
Cook for 2-3 minutes, until edges are browned and crispy.
Flip patties. Top each with a slice of cheddar cheese. Cook for another 2-3 minutes, or until cheese is melted and patties are cooked through.
While burgers cook, lightly butter the cut sides of the brioche buns and toast them on the skillet until golden brown.
Assemble burgers: Spread chipotle whiskey sauce on the bottom bun. Add the smash burger patty, followed by 1-2 slices of bacon. Top with the other half of the bun.
Notes
For extra crispy edges, do not overcrowd the pan when smashing.
Adjust chipotle and whiskey amounts to your preference.