Chhurpi, or durkha, is an extremely hard cheese native to the Himalayas, traditionally made from Yak's milk or buttermilk (ours is made from a blend of both). The milk gets boiled, then the curds are wrapped in a thin cloth and hung out to dry for several days. Once the cheese is quite firm, it's sliced into strips or cubes and dried over a fire or in an oven on low heat.