Byaslag - Бяслаг (Cheese from milk of cattle, yaks, goats, or sheep)

Most commonly, the milk of yak and cattle is used. Goats and sheep are not milked in all places, but make for the most aromatic cheese. However, mongolian cheese doesn't get to ripen like its european counterparts, so the overall taste is somewhat bland in comparison.

Preparation
Boil the milk, and add a small amount of kefir (instead of rennet). After the milk has curdled, lift out the solid components with a large cloth. Let most of the remaining liquid drip off, and press the mass between some wooden boards with a weight. The resulting "wheels" of cheese will have a round or approximately square shape of about 25 cm diameter and 5 cm height.

In a nomadic household, it is not possible to let the cheese ripen as it is done in the european tradition (storing, turning, salting, etc.). Instead, you can cut it into slices and dry them for better preservation.
Use

Fresh slices of cheeses are eaten as a snack. Dried cheese is rather hard, and often gets soaked in tea. Pieces of cheese may also be given into a soup.

Aaruul - Ааруул "Dried curds"

Leave the milk (usually from cattle, yaks, camels) to curdle. Lift out the solid components with a fine cloth and let as much of the liquid drip off. Then press the mass into a cake of a few cm height between two wooden boards, weighted down with stones.

Cut the solid cake into pieces of about 10 length. Arrange the pieces on a wooden board and put them into the sun for drying. In Mongolia, this happens on the roof of the yurt. A cover of fine white cloth will keep the birds away.

Use
The dried pieces can be stored almost indefinitively. They can get quite hard, so most people rather suck than bite on them. The taste may vary regionally and depending on the milk used, but usually includes a combination of sweet and sour.

Arul belongs to the most common travel provisions (next to Borts). The pieces are also a ready snack for the small (or larger) hunger at almost any time. Some sources cite Aaruul as the primary reason that traditionally living mongolian people have very little troubles with their teeth. It is also one of the core vitamin sources for the nomads.
Korkhoi Aaruul

"Worm Aaruul" is a variation in the shape of little strands, often sweetened. Don't press the fresh material, but put it through a meat grinder (available in every mongolian houshold) into small "worms". Arrange those in little heaps for drying. This type of Aaruul is easier to chew (especially for children), but less suited for travel supplies.

Urum - Өрөм "White butter", clotted cream

The milk of yaks (or in the Gobi camels) is best, because it contains more fat. The first few pictures show the production of Urum from yak milk.
Preparation

Heat the milk on the stove, just below boiling. In regular intervals, lift a ladle full into the air, and let it splash back into the pot, to create foam. This "scooping" (самрах) is necessary because the shallow wok-like Mongolian pan makes normal stirring ineffective, but it also has the quality of a ritual.

Once there is enough foam, let the milk cool down slowly. Now it needs to rest overnight. In the morning, a skin of about 1 cm clotted cream has formed, which is taken off. Stored dry and cool (in a wooden vat or a sheep's stomach), Urum will stay palatable for a full winter season.

Cattle milk contains less fat, so the skin will be thinner. The following images show the resulting smaller amount of Urum.