1 pound 100% ground chuck, ground once and loose packed, formed into 4oz patties, 5" wide
8 slices of American cheese
Thinly shredded iceberg lettuce
1 pound yellow onions, sliced
1/3 cup sherry vinegar
Potato rolls, 4" each
3 tablespoons butter
1/2 cup mayo
2.5 tablespoons cornichons, minced
2 teaspoons shallots, minced
1 teaspoon mustard
1 teaspoon Worcestershire
2 tablespoons ketchup
Butter all the buns and toast in a medium high cast iron skillet, till super toasty, set aside.
Season the burger patties.
Get the cast iron skillet hot to medium/high heat. Place a big old knob of butter in the pan.
Place patties in the pan and cook 2-3 minutes each side making sure to get a great caramelized crust on at least one side.
Place two pieces of cheese on each patty after the first flip.
Mix mayo, cornichons, shallots, mustard, Worcestershire, and ketchup
In a pan on medium heat, place 1 tablespoon of butter and caramelize onions gently for about 10 minutes, deglaze with sherry vinegar and let reduce to almost dry, season with salt and pepper. Set aside.
Place a 1 tablespoon of special sauce on each bun, caramelized onions on the bottom bun, lettuce on top of the onions, burger patty on top of the lettuce, and then top with the other bun.