Soak urad dal for 8 hrs. 2 hrs before grinding soak Idli ravva. After 8 hrs grind urad dal to fine batter. Sqeeze out water from idli ravva and mix both urad dal batter and idli ravva. Add 3tsp salt. Add little water should be thick.

Ferment for 10 to 12 hrs. Batter will double. Whisk well. Grease idli plates and fill with batter. Steam cook for 15mn. Serve with sambhar. Recipe of sambhar I have given in my previous posts.