Cordyceps is a group of parasitic fungi prized in Chinese and Tibetan medicine, most famously the wild caterpillar fungus Ophiocordyceps sinensis, which grows from the mummified body of a moth larva high on the Tibetan Plateau. Earthy, faintly sweet and mushroomy, it is brewed into tonic teas, simmered in soups and stewed with meat as a restorative, and is one of the most expensive biological commodities on Earth.