Suja is made by brewing black tea very strongly, then pouring it into a long wooden churn along with a large spoonful of yak butter and a pinch of salt. The mixture is pumped back and forth in the churn until it is creamy and well blended — a bit like how cream turns into butter when you shake it. The result is a pale golden drink with a smooth, slightly oily surface.
For many Bhutanese people, suja is the very first thing drunk in the morning. It is offered to every guest who visits a home as a sign of welcome. Refusing it can sometimes seem impolite, so visitors often accept a cup even if they have never tried anything like it before. Hosts keep refilling the cup, so it is polite to leave a little at the bottom to signal you have had enough.
Yak butter is the key ingredient, and yaks themselves are central to life at high altitude in Bhutan and the wider Himalayan region. Yaks produce rich, fatty milk that is perfect for making butter, cheese and suja. The butter can be stored for a long time in cold mountain conditions. Yaks also carry heavy loads, provide wool for weaving, and are a symbol of the hardy mountain lifestyle of the Himalayan plateau.