Chhurpi is a Himalayan yak-milk cheese made across the high country of Nepal, Bhutan, Sikkim and Tibet, produced in two very different forms: a soft, fresh, tangy cottage-like cheese used in cooking, and a rock-hard, smoke-dried version that is famous as one of the world's longest-lasting chewable snacks. The hard form is prized as a slow-release chew that softens for hours in the mouth, tasting mildly smoky, savoury and faintly cheesy.