Stir together the mayonnaise, ketchup, mustard, and pickle brine in a small bowl. Taste it and adjust to your liking. Set this aside in the fridge while you cook.

Divide the ground beef into 8 equal balls, about 3 ounces each. Do not season them yet. Set them on a plate and have your salt, pepper, spatula, and cheese slices all within reach before the skillet gets hot.

Heat a cast iron skillet over high heat for about 2 minutes until it is very hot and just starting to smoke lightly. You want serious heat here so the beef gets a real crust. Do not add oil. The fat in the beef handles that.

Working in batches of 2 or 3 balls at a time so you do not crowd the pan, place a beef ball in the skillet and immediately press it flat with your spatula as hard as you can. Season the top with a pinch of salt and pepper right now. Let it cook undisturbed for 2 minutes. You will see the edges turn brown and the top start to go gray. That is your cue.

Flip each patty with a firm scrape of the spatula to get all those crispy bits. Lay a slice of American cheese on top of each one right away. Cook for 1 more minute until the cheese is melted and gooey. Repeat with remaining beef balls.

Warm the flour tortillas directly on the hot skillet for about 20 seconds per side, or wrap them in a damp paper towel and microwave for 30 seconds.

To build each taco, spread a spoonful of special sauce down the center of a warm tortilla. Lay one cheesy patty on top, then add a small handful of shredded lettuce and a few pickle chips. Fold the tortilla around it and serve immediately while the beef is still hot and the cheese is still melted.