Ask any self-respecting Louisianan who makes the best gumbo and the answer is universal: "Momma." The product of a melting pot of culinary influences, gumbo, in fact, reflects the diversity of the people who cooked it up: French aristocrats, West Africans in bondage, Cajun refugees, German settlers, Native Americans--all had a hand in the pot. What is it about gumbo that continues to delight and nourish so many? And what explains its spread around...