Boil 0.25 liter of milk during 5-7 minutes, pour into a glass jar, cool up to 40-42 degrees in the summer and 43-45 in the winter, add the pack of Narine to the milk, mix, close the cap of the jar, wrap with paper and after wrap with woolen blanket and leave for 5-7 hours until it becomes thick, after that put it into the refrigerator. After 2-3 hours, take one tablespoon of middle layer of leaven for one liter of milk, and the other part is ready for using. During the first 2 days give to child 2-3 tablespoons on the 3th day 100-120 ml. Heat it up using water bath before feeding. If it is necessary, add a little sugar. After 3-4 consecutive leavens you have to make a new leaven.