This empire started out as a New York hot dog cart and didn’t even sell burgers until three years in. Now they do made-to-order burgers, crinkly fries, and “concrete” milkshakes, and it all has a cult-like following. Get the classic Shack Burger with fries and a Vietnamese Coffee & Donuts concrete, made with “Cop” donuts from Morningstar and cafe sua da marshmallow sauce.