For the smash sauce: Mix together the mayonnaise, gherkins, ketchup, sriracha, mustard, granulated garlic and 1/4 teaspoon pepper in a medium bowl. Season to taste.
For the burgers: Heat a large flat-surfaced griddle pan to high heat. Add the vegetable oil.
Add the balls of meat to the hot griddle and let cook for 15 to 30 seconds. Flip the burgers and, using a trowel or large spatula, smash each ball of meat until about the size of the bun (the overhang is crucial). Smash and schmear down the edges of the beef even further, so that they are a little thinner than the middle. Sprinkle the exposed side with salt, pepper and a little granulated garlic. Cook until super dark and caramelized, 1 to 2 minutes. (The beef will release better when properly caramelized.) Now it's time to scrape the beef and flip, ideally using a griddle scraper or paint scraper to get up every bit of beef. Immediately top each patty with 2 slices American cheese and sear for another 1 to 2 minutes. Spread 1 tablespoon butter on each burger bun and place on the grill. Cook until lightly toasted, 1 to 2 minutes. Top each bun with a patty, lettuce, tomato and smash sauce. (I like mine plain, with a smash sauce dunk.)