Insisting that you cannot get a decent one outside of New York, and possibly one bakery in Israel, Sheraton is almost decadent in her connoisseurship of bialys. So are the aging remnants of Bialystok's pre-War Jewish community, now scattered everywhere from Argentina to Australia, who deplore what they see as a modern tendency toward undercooked bialys with stale onions and, shockingly, no poppy seeds. Their homespun reminiscences about the everyday rituals of making, buying and relishing this unprepossessing foodstuff are vivid and affecting. In a quiet way, they remind us of what was lost in the catastrophe.