Soak the dals with with 4 cups or more water enough to cover the dal and soak it . Cover the bowl with a lid and let it stand for 4-5 hours , best is overnight.
Drain the water if in excess and grind the dal in small batches depending on the size of your grinder .
Grind well to form a smooth batter . Add a tablespoon or 2 water to aid grinding if necessary. The batter is pancake / medium cake batter consistency. Let the batter stand for 15 minutes and then the batter is ready for use.
Add salt just before making the dosas . Dosa batter can be spiced up as well.
Now, heat up the non-stick pan. Before spreading the batter, sprinkle cold water and bring the temperature of the tawa down so that the batter can be spreaded easily.
Pour about 1/2 cup of batter in the middle and spread from center to out thin using ladle spoon. If desire, smear few drops of oil to make dosa crispy.
Cook Dosa till golden brown. Usually one side of the Dosa is cooked but for extra crunch, you can bake Dosa on both sides.
When done, remove from the pan and serve with Chutney or left over Pav Bhaji.