Use your hands to mix the ground beef, Worcestershire sauce, garlic powder, salt, and pepper in a medium bowl. Form 8 patties, each about 4 inches wide and ¼-inch thick.
Cut each slice of cheese into 4 equal sized squares and stack each set of 4 pieces on top of each other. Place a stack of cheese on 4 patties. Cover these patties with the remaining patties, sealing the cheese inside by pinching the edges with your fingers and smoothing out the shape of the burger with your hands.
Heat the oil in a cast iron pan over medium-high heat. Cook the burger until it’s brown and griddled on the underside and doesn’t stick to the pan much, about 4 to 5 minutes. Carefully flip it and repeat on the other side.
Let the burgers rest for a couple of minutes before eating, because the hot cheese could scald your mouth. Serve on buns with your choice of condiments, such as caramelized onions, pickles, iceberg lettuce, ketchup, and mustard.