Byaslag is a mild, unripened Mongolian cheese prepared from the milk of yak or cows. The milk  is heated over a gentle fire, and then a curdling agent such as whey or yoghurt is added gradually to the milk, causing it to separate. During this process it is important to regulate the temperature of the milk and the quantity of curdling agent, as too much of the latter can produce a bitter-tasting cheese, while too little can result in the incomplete separation of the curd. Once the curd has properly formed it is drained and wrapped tightly in a cloth or put into a cotton sack, then placed between two flat boards with a heavy weight over the top, and left until the remaining whey has been squeezed out. Byaslag is mostly consumed during travelling or weddings and festivities or is offered as food to visitors.