Yellow tea is one of those teas that you hardly ever find in a non-specialist tea shop because it is produced in really tiny quantities.
The small amounts that are produced are usually given or sold to rich Chinese clients as Yellow tea continues to have an image of exclusivity ever since the days when it was reserved as an imperial tribute tea for the Emperors of China. If a supplier can get hold of any Yellow tea then they have to make sure that they are not being palmed off with the leftovers but can get the high end leaves too.
A good quality Yellow tea takes a lot of work to make properly. The process mimics that of green tea - picking, withering and pan frying but afterwards the leaves are kept hot in a moist environment (usually covered).
This allows the leaves to release and reabsorb moisture, a kind of breathing process which the Chinese refer to as 'reabsorbing essence'. The leaf loses its green colour in favour of a yellow and the flavour changes.
Yellow tea is like drinking an extremely delicate and light green tea. It has less of the vegetal, umami notes and less of the cut grass green elements. They are replaced with a brew of unparalleled purity, like drinking fresh morning dew. The tea is soft, slightly sweet and retains a delightful whisper of the green tea freshness. The finish of a yellow tea is supposed to be very smooth.
The two main types of Yellow tea are Huo Shan Huang Ya (Amber Mountain) and Jun Shan Yinzhen. The latter is more expensive and because it is produced in silly small quantities, the majority of Jun Shan Yinzhen that is sold overseas is a pale imitation of the good stuff with a hefty price tag so be careful when buying!