During the scene, Chef Slowik (Ralph Fiennes) presses a ball of ground beef into a steaming hot griddle, adding a few grinds of pepper and a thin sliced white onion on top. John Benhase, a consulting chef on the film, says that smashing the beef balls down into a thin patty causes the fat to render and the meat to crisp and caramelize, but the key to this outstanding burger is the use of onions.