DISAPPEARING DISHES.(cataloguing regional Mexican cuisine)

In a peaceful town perched high on the rolling brown hills of Oaxaca, Diana Kennedy, cook, writer, and foremost authority on Mexican food, is hard at work on her latest research project. In a white shirt with rolled-up sleeves, khaki trousers, and comfortable shoes, she peers intently over the top of her reading glasses at her subject, a shy, elderly Mexican housewife named Clementina Banos. Kennedy questions her in a way that manages to be friendly and utterly efficient at the same time. "So, Senora, do you let the tomatoes cook a little with the onion before you put in the fruit? For how long, would you say? Ten minutes? Until they dry up a little? And then the fruit is ...