When Laura Silver's favorite knish shop went out of business, the native New Yorker sank into mourning, but then she sprang into action. She embarked on a round-the-world quest for the origins and modern-day manifestations of the knish.

The iconic potato pie leads the author from Mrs. Stahl's bakery in Brighton Beach, Brooklyn, to an Italian pasta maker in New Jersey--and on to a hunt across three continents for the pastry that shaped her identity. Starting in New York, she tracks...