The hunt for a fungus that is worth more than its weight in gold as a traditional medicine is transforming the Himalayan landscape on which it grows. To learn more, I have come to the Sowa Rigpa Institute of Traditional Medicine in Kathmandu, Nepal, where I am watching the preparation of a tea made from yartsa gunbu, a "cure-all" fungus that may be the world's most expensive natural resource. Tsultrim Rabsel grinds and mixes the fungus with 16 rare herbs and medicinal plants. He hands a tea sachet to Tashi Tsering, who carefully places the grinds within. "Medicine's ready," he says.