8 slices American, cheddar, or Swiss cheese (about 6 ounces)
4 (4-inch) hamburger buns, split
Ketchup, mayonnaise, mustard
Divide the meat into 4 equal portions. Shape each portion into an even 1/2-inch-thick patty that is about 1 inch wider in diameter than the hamburger buns. Using your thumb, make a shallow 1-1/2-inch wide indentation in the center of each patty. Transfer the patties to a plate and refrigerate while you prepare the grill.
Heat a grill pan or outdoor grill to 600°F to 800°F. When the grill is ready, use tongs to rub the grate with several layers of paper towels dipped in vegetable oil.
Season the hamburger patties generously on both sides so that you can see a thin layer of salt and pepper. Place the patties on the grill indentation-side up, cover the grill, and cook the patties undisturbed (do not press down on them) until grill marks appear on the bottom, about 3 to 4 minutes. Using a spatula, flip and cook for about 2 minutes more. Place 2 slices of cheese on each patty, cover the grill, and continue cooking until the patties are just slightly pink in the center for medium, about 2 to 3 minutes more. Remove to a clean plate and let rest in a warm place or tent loosely with foil.
While the patties are resting, place the bun halves cut-side down on the grill and toast until golden brown, about 1 minute. Remove the buns to a clean serving plate, place a patty on each bun bottom, garnish as desired, and cover with a bun top.