Thanks to Cesar Moncloa Guardia for the beautiful photo.
The name of this unique ingredient comes from the Quechua ch´uñu, which literally means freeze-dried potato. Chuño is made with regular potatoes which are dried in the heights of the Andes. This word, however, refers to two different things in Peru: 1- It is a potato starch used as a thickener in several sauces, cakes, and desserts. 2- It is a freeze-dried potato whith a long shelf life, and can be used in several stew and soup recipes.
In the market, you can find white and black chuño. The latter is made with bitter potatoes, which are left to freeze overnight in the open air. In the morning, they thaw under the sun, and then they are crushed to extract their liquid, and frozen all over again at night. This process is repeated many times until the potato is completely dehydrated. To make white chuño, on the other hand, potatoes are soaked in the icy cold water of rivers and streams for several days, and then sun-dried.
Chuño has an extremely long shelf life (it lasts for several years), and it has been part of the Andean diet for centuries. To consume it, you need to rehydrate the dried potatoes by soaking them in water. Then they are mainly used to make Andean soups and stews, or you can just cook them and eat them with corn and cheese.