Airag

Pour the fresh milk into a large clean container or traditional leather bag. If using cow's milk as a substitute, warm it to body temperature first, then add the kefir grains or starter culture and stir thoroughly to distribute evenly.

Seal the container loosely to allow gases to escape during fermentation. Place it in a cool area at approximately fifteen to twenty degrees Celsius, away from direct sunlight, where it can ferment undisturbed for the initial phase.

Stir or agitate the fermenting milk vigorously four to six times throughout each day. Traditional Mongolian practice requires anyone passing the container to give it several strong stirs, which promotes even fermentation and develops the characteristic fizz.

Continue the fermentation and regular stirring process for two to three days. The milk will gradually thicken slightly, develop a pleasantly sour and tangy aroma, and become mildly effervescent as natural sugars convert to lactic acid and trace alcohol.

Taste the airag daily after the second day to check fermentation progress. It should have a refreshing sour tang similar to buttermilk with gentle carbonation. When the flavour reaches your preferred balance of sourness, the airag is ready to serve.

Strain the finished airag through a fine cloth if desired to remove any lumps, then transfer to clean bottles and refrigerate to slow further fermentation. Serve cold in bowls as a traditional Mongolian beverage alongside hearty meals.