Grind soaked Urad dal with little water and make a smooth paste. Pour the paste in a big mixing bowl. In the same grinder, grind soaked rice and cooked rice together with little water. Add enough water for it to be able to grind. Grind till becomes a fine paste. Pour the batter into a mixing bowl, then add urad dal paste to it. Mix well, and keep it in a warm place over night for fermentation.