Divide the ground beef into 4 equal portions (about 6 ounces each). Do not overwork the meat.
Preheat a cast-iron skillet or griddle over medium-high heat. Add vegetable oil.
Place the beef portions onto the hot skillet, leaving space between them. Immediately smash each portion flat with a sturdy spatula or burger press.
Season the smashed patties generously with salt and pepper.
Cook for 2-3 minutes per side, or until a deep brown crust forms and the patties are cooked through. Avoid pressing down on the patties after the initial smash.
During the last minute of cooking, place a slice of cheddar cheese on each patty and cover briefly to melt.
While the burgers are cooking, lightly toast the burger buns on the skillet or griddle.
Assemble the smash burgers with your favorite toppings and serve immediately.
Notes
For an extra flavor boost, you can mix a little Worcestershire sauce into the ground beef before forming the patties.