For high-rolling, peripatetic gourmands who've already ticked off the checklists of the world's destination restaurants, the expanding calendar of culinary festivals offers another ideal way to stimulate the curious palette. For starters, there's a virtual guarantee that headline chefs like Nobu Matsuhisa or David Bouley will be cooking dinner themselves rather than leaving the work to gifted minions. Master classes can show you how to produce espumas with studied nonchalance and learn the newest culinary techniques as they emerge from the fervid imagination of Ferran Adrià or Heston Blumenthal. What's more, says René Redzepi, trailblazing chef at Noma, Copenhagen's first two-star...