Divide beef into 8 even portions, about 3 oz each. Loosely roll them into balls then cover and refrigerate while preparing the remaining ingredients. The meat must be cold when it hits the grill.
Remove wilted leaves from lettuce to keep it crunchy then finely shred lettuce. Slice tomatoes, onions, and pickles.
Butter and toast buns over medium heat until golden on the buttered side.
Increase griddle to medium/high heat. Place 2-4 burger balls onto a hot griddle. Working quickly, place parchment paper over the meat and firmly smash straight down into a thin patty.
Once patties are smashed, peel back and discard parchment papers and season patties with salt, pepper and garlic powder. Add 1/2 teaspoon of burger sauce. Cook 2 minutes on the first side or until seared and juices start to come to the surface.
Scrape under the burger with a spatula facing down at a 45˚ angle to get under the caramelized part and flip. Cook another 1 minute. The top half of the patties with sliced cheese and cover the cheese with the second patty. Repeat with remaining burgers and transfer them to a platter as they finish cooking.
Place sauce on the bottom of the bun. Top with 3 pickle slices, shredded lettuce, 2 tomato slices and thinly sliced onion. Add double patty and top with bun.
