Many credit the french dip to Philippe Mathieu, owner of L.A.'s Philippe the Original. In 1918, Mathieu was making a roast beef sandwich when he accidentally dropped a baguette in his roasting pan. The prep hasn't changed much since then: Rolls get a two-second bath in beefy juices before they're piled with roasted prime rib, smeared with spicy mustard, and plated with a dunking bowl of hot broth ("au jus").
