Preheat a cast-iron skillet over high heat for about 5 minutes until blazing hot.

Form the cold ground beef into loose balls—about the size of a golf ball—without overworking the meat.

Place the beef balls into the hot skillet and smash each ball down into a flat patty. Cook for 2-3 minutes until the edges crisp up.

Season the patties with salt and pepper, then flip them and add a slice of pepper jack cheese on top of each patty. Cook for another 2-3 minutes until the cheese melts.

Remove the patties from the skillet and let them rest for about 2 minutes. Warm up the burger buns in the same skillet.

Spread mayo on the bottom half of the warmed burger buns, then place a cheesy beef patty on top, followed by fresh jalapeño slices. Add any additional toppings you like.