Clean and soak urad and moong dal (together in a bowl) and the rice(in another bowl) in water for two hours.

Grind the dals  with salt, green chillies and ginger and  water to a smooth paste. At this stage, add the rice and grind further until the entire mixture is ground to a smooth paste (about 5 min). The dosa batter should be thinner than the batter consistency for masala dosa but thicker than the neer dosa batter.

Store the batter at room temperature for 12 hours (for the batter to ferment and rise). If the dosas have to be made later than 12 hours, then the batter can be stored in the fridge (lasts up to 3 to 4 days in the fridge and for a few weeks  in the freezer.  The batter should be at room temperature, to reuse it).

At the time of making the dosa, add the jeera seeds to the batter

Heat a flat, ten inch skillet/tava on a medium flame  and pour 1/4 cup of batter on to the center of the tava. With the back of a large spoon or ladle, spread the batter in a circular manner out to the edge of the pan to make a thin round dosa.  Take 1/2 a tsp of oil and dot it on top of the dosa and around the edges.

Close the lid  and cook for less than a min. Remove the lid and if you want a extra crisp dosa, flip the dosa over and cook for a few seconds more. Remove from skillet/tava. Place on a plate. Serve with chutney or any gravy dish(koorma, huli, sagoo...)