Tortilla española exists in almost every corner of Spain: as a tapa in fancy city restaurants; as a filling for bocadillos (sandwiches) at gas-station cafés; as a main course served on worn metal plates in home kitchens. Mario Batali’s version, based on one he tasted in the Ribera del Duero wine region, is baked until golden brown and offers an especially high ratio of potatoes to eggs.