Start by boiling the milk on high heat in a non-stick pan.
Reduce heat to medium and stir constantly. Stirring constantly is very important as this prevents milk from sticking to the bottom and burning. In-case it burns or sticks and forms skins, do not worry, filter it through a sieve immediately and move to a fresh and clean non-stick pan. By doing this you also prevent the milk from the burnt smell and bitter taste.
Continue stirring till it reduces and thickens.
After about 3 hours of stirring, when the milk is considerably reduced and browned (by the caramelisation of the sugar in the milk), add brown sugar and stir for another 30 minutes till it becomes thickened.
Pour it into a 24cm x 15cm x 5cm baking tray. Cut into desired shapes and allow to set in the fridge for atleast 30 minutes.
Or if you choose make small roundels of golf ball size.