Divide the beef into 4 equal portions and press each into a flat patty about 4 inches wide and 1/2 inch thick. Season both sides with salt and pepper.

Heat a cast iron skillet over high heat for 2 minutes until it just starts to smoke. Cook the patties for 2 minutes on the first side, flip, top each with 1 slice of American cheese, and cook for another 1 to 2 minutes on medium-high heat until the cheese is melted and the internal temperature reaches 160°F (71°C).

Place the buns cut-side down in a dry pan over medium heat for about 1 minute until lightly golden.

Spread 1 tsp ketchup and 1/2 tsp mustard on the top half of each bun. Add 4 pickle chips, a pinch of shredded lettuce, and 1 slice of onion to each bottom bun.

Set a cheesy patty on each dressed bottom bun, press the top bun into place, and serve immediately.