Saffron is the world’s most expensive spice: a testament not only to the labor required to produce it, but to its unique ability to impart both an unusual flavor and an intense yellow color to foods. It is a part of the flower of a kind of crocus, Crocus sativus, which was probably domesticated in or near Greece during the Bronze Age. The saffron crocus was carried eastward to Kashmir before 500 BCE; in medieval times the Arabs took it westward to Spain, and the Crusaders to France and England. (The name comes from the Arabic for “thread.”) Today Iran and Spain are the major producers and exporters. They use saffron in their respective rice dishes, pilaf and paella; the French in their fish stew, bouillabaisse; the Italians in risotto milanese; the Indians in biryanis and milk sweets.