Rinse and soak rice, aval and urad dhall in water for 1 hour. Wet grind the above with salt into a nice batter. Keep at room temperature for 12 hours. Method to make Aval Dosai: Spread a big spoon full of the above batter on a hot non-stick pan, and put 1 t.spoon of oil around it. Close the dosa with a cover and let it cook for a few minutes. Do not turn the dosa. Serve it hot with chutney.