Put the milk in a kadhai, wok or deep, heavy-based pan.
Bring to the boil.
Reduce the heat to low and cook, stirring after every 5 minutes until the milk is reduced by half.
Stirring constantly and continually scraping in the dried layer of milk that sticks to the sides of the pan, continue to cook until reduced to a mashed potato consistency.
Transfer to a bowl and continue to cool.
When cool, this paste can be stored in the refrigerator for upto 2 days.
It can also be dried and stored as a solid.
Spoon the paste into a clean piece of muslin (cheesecloth).
Then place in the sink weigh down with something heavy and leave to drain for about 1 hour.
The resulting solid should be stored in the refrigerator, and can be grated or crumbled as required.