Anthony Bourdain was an unknown cook plating steak frites when his mother sent David Remnick his essay about what really goes on in the kitchens of New York restaurants. After The New Yorker published it, Bourdain wrote the ribald memoir “Kitchen Confidential,” and a celebrity chef was born. Now, he hosts “Parts Unknown,” a food show with a very different approach from most. Bourdain visits countries all over the globe—including some that we rarely see on the news—and he relishes not only in their cuisines but in their people, customs, and politics. He tells Remnick about filming an episode in Hanoi, where he and President Obama—a notoriously careful eater—drank beer and chowed down on bún chả, a local street-food favorite.