Droma roots
Dried tiny root tubers of silverweed from the Tibetan highlands, barely the size of a fingertip, with a sweetish, nutty flavour.
Droma are the tiny, swollen roots of silverweed (Potentilla anserina), gathered on the Tibetan plateau and dried. They taste mildly sweet and nutty, somewhere between chestnut and sweet potato, and turn tender when cooked while keeping a slight bite. In Tibetan cooking they are a festive ingredient, especially at New Year, when they are served with rice, butter and sugar. Dried droma are often gritty and are washed thoroughly, then soaked or simmered until soft before use. They are found almost only in Tibetan or Nepali shops and through mail order, rarely in a well-stocked Asian grocery.
Substitute:
There is no real substitute. Small cubes of cooked chestnut come closest to the nutty sweetness, but they are mealier and softer and do not give the small, firm morsels that define the dish.