Yak butter is butter made from the milk of a yak, a grass-eating mammal that lives on the Tibetan plateau. It is most commonly consumed in Tibet in a mixture called yak butter tea, where it is found mixed with hot black tea. Most yak's milk is used to make butter, but it can sometimes be used to make yogurt or cheese. Yak butter is not used in many dishes, and aside from its used in yak butter tea, it is mainly used as lamp fuel, as moisturizer for skin, or to tan animal hides.
This type of butter bears many similarities to the common butter from cow's milk that many people know, but it does have some major differences. Like cow's milk butter, butter from yak's milk is made by churning the cream from yak's milk until it takes on a thick, solid texture. Churning means mixing or shaking the cream or milk to help it turn into butter. This is usually done by stirring it with a wooden paddle or shaking it. Butter from yak milk is often shaken inside the stomach of a sheep.
Unlike cow's milk butter, yak milk is fermented overnight or for a few days before it is churned. Since yak butter is higher in fat than cow butter, it is much more dense and has a texture similar to cheese. When yak butter is brought to market for sale, it is often transported wrapped in yak skins, which protect it from spoiling. This type of butter forms blue veins as it spoils. It spoils more slowly when refrigerated or in cooler, drier climates.
The most common way this butter is served as food is in a unique type of tea. Butter tea typically has a large amount of butter in it, which is blended into hot brewed tea by shaking the mixture. The butter in the tea is often salted before mixing it with the tea. This preparation for tea contains a large amount of yak butter.
Generally, yak butter tea is an acquired taste as it has many flavors and textures most people are not used to. This tea is salty, and it often has a flavor that some consider rancid. The butter in this tea is not always rancid, but it is frequently served that way. It also has an oily, thick, lumpy texture that some people find disagreeable.