This is the traditional, griddled hamburger of diners and takeaway spots, smashed thin and cooked crisp on its edges. It is best to cook in a heavy, cast-iron skillet slicked with oil or fat, and not on a grill. For meat, ask a butcher for coarse-ground chuck steak, with at least a 20 percent fat content, or grind your own. Keep it in the refrigerator until you are ready to cook, and try not to handle it with your fingers — use an ice-cream scoop or spoon instead. Plop down a few ounces in the pan, smash it with a spatula, salt it, let it go crisp and flip. Add cheese and get your bun toasted. The process moves quickly.