Prepare the Beef
Place the ground beef in a mixing bowl. Add the Worcestershire sauce and garlic powder, then gently mix with your hands until the seasoning is evenly worked into the meat.
Shape the Portions
Divide the beef mixture into 8 equal portions and roll each one into a small ball, about 2 ounces each.
Heat the Cooking Surface
Set a large cast iron pan or flat-top grill over high heat. Let it get extremely hot before adding the beef. A flat-top lets you cook everything at once, but a skillet works too—just plan to cook the burgers in a few rounds.
Smash and Season
Place the meat balls onto the hot surface. Right away, press each one down firmly with a burger press or two spatulas until very thin. Make each patty slightly wider than the bun since it will shrink as it cooks. Season the tops with salt and black pepper.
Cook the First Side
Let the patties cook for 45 to 60 seconds, until the edges look crisp and browned and the tops begin to lose their raw color.
Flip and Add Cheese
Turn each patty over, then season the second side with a little more salt and pepper. Quickly place a slice of cheese on every patty while they finish cooking.
Build Double Patties
Stack 4 of the patties on top of the other 4 to make 4 double cheeseburger patties.
Assemble and Serve
Transfer the burger stacks onto the toasted buns. Add lettuce, tomato, pickles, onion, and smashburger sauce, then serve right away while hot and juicy.