Churtsi is a yak cheese made in Bhutan.
It can be made from milk from a dri (female yak) or from a chauri (a cross between a cow and a yak.)
To make chursti, a yoghurt which they call “dhai” is first churned for butter. The remaining buttermilk is heated until it curdles. The curds are strained out, and then hand formed into small balls which are then put into bags and hung over fires to smoke.
The cheese ends up hard and rubbery with a strong, smoky flavour.
It can be stored for several years with no noticeable change in taste, texture or appeal.