Truffle. Fine Champagne. Goose fat. These are just some of the ingredients of the world’s most costly fries, served up at New York City’s Serendipity 3 restaurant. "It's a thrice-cooked process. We do a first blanche inside Dom Perignon and a French champagne vinegar,” said Corporate Executive Chef Frederick Schoen-Kiewert. The restaurant is also home to the world’s most expensive burger and ice cream sundae.