Soak rice and black gram overnight and grind to make a smooth batter. Add salt in to it and leave it for one hour. Add enough water to make a watery batter. Fry grated coconut and sugar in a pan. Add crushed cardamom in to it and fry for 1 min more. Heat & grease the tawa, then twofold a muslin cloth, dip it in the batter and make a cross structure in the tawa. Put little stuffing in the middle of it and fold it from 4 sides to make a square size. Then take out the Chhunchi Patra pitha carefully.