Chef Uncovers In-N-Out Burger Secret

East-coasters who have long envied the West Coast’s In-N-Out Burgers may soon be able to make their own: Josh Chapon, the chef of Lure, snuck into a kitchen at Las Vegas’ In-N-Out and says he discovered the restaurant’s secret ingredient: a smear of mustard on the patty on the grill, right before he flips it. According to Chapon, the mustard cooks off but the flavor remains.