Place cast-iron skillet over medium heat 5 minutes before cooking the patties.
Roll 6-ounce (170 g) burger balls from the brisket and pat them into flat, thick patties, about 1 inch (2.5 cm) thick. Season the patties with salt and pepper.
In a bowl, combine the pickles and mayonnaise; set aside.
Place three patties in the skillet (with no oil). The fat will render and you will have a juicier burger from the natural fat inside the patty. Cook for 4 minutes on one side, then flip.
Top each patty with the jam and then put 2 slices of cheese per patty on top. Pour 2 tablespoons water into the skillet, covering it immediately so the burgers can steam. Remove the lid after 45 seconds. The cheese should be fully melted.
Butter the buns and place them face down in another skillet over medium high heat so they get nice and toasty.
Spoon the pickle mayo on the bottom buns, then add a good pile of the lettuce. Add the cheesy beef patties, cover with more of the pickle mayo,then add bun tops.