The tea, brewed in water, comes from bricks of tea has been a major trade item for over 800 years. The brewed tea is poured into a long cylindrical churn make of wood banded with brass, along with salt and a small lump of butter. After vigorous churning, the opaque liquid is decanted into a teapot or a thermos, where it is kept for drinking throughout the day. The resulting drink is more like bouillon than tea as Westerners or Chinese know it. The body needs this extra fat intake to power its higher metabolic rate at high altitude, especially in cold weather.
Tea provides a constant source of hydration and is everywhere socially important.
The best tsampa, like good coffee, is fresh-roasted and ground, enough for a week at a time, and has a nutty flavor. The milk from the evening milking is boiled, left in a pail overnight to turn into yoghurt, and mixed with boiled milk from the following morning's milking before being churned. It is this half-yoghurt mixture, not rancidity, that gives Tibetan butter its strong taste. In eastern Tibet, the evening and morning milk are churned separately to produce sweet butter, sometimes also found in the street market in Lhasa. In some low valleys around Lhasa, the milk comes from recently introduced cattle herds.