AMHERST - Joan Nathan is a public television star and cookbook author whose specialty is Jewish food from around the world. She is visiting the National Yiddish Book Center here for a day of cooking and kibitzing with an intimate crowd, over recipes from her latest book, “Quiches, Kugels and Couscous: My Search for Jewish Cooking in France.’’ The center’s kitchen is perfumed with the sweet scent of freshly baked anise challah. Earlier, Nathan taught participants how to make the handsome loaves, their crusts golden and gilded with egg glaze. The multigenerational group includes pairs of mothers and daughters who gather around to soak up the culinary wisdom of the globe-trotting culinary maven.