Add rice and millets/ bajra to a large pot and wash them well at least thrice.
Add water and soak them for at least 4 hours.
Add urad dal to another pot. Wash it well and soak for 4 hours.
Drain the water from both the pots.
Add dal to a blender jar along with water just enough to blend. I used about ¾ to 1 cup.
Blend it till smooth and frothy. Transfer it to a large bowl.
Add rice and kambu/ bajra to the same jar along with little water. Blend it well until smooth.
Mix together the batter. If you live in a cold place you can add non iodized salt at this stage. Cover the bowl.
Ferment it in a warm place for 6 to 8 hours or as needed.
After fermentation the batter rises well and turns light. Add salt if you have not added before fermenting. Add little water to bring it to a consistency. The consistency must be neither too thick nor too thin (runny). It must be of spreading consistency. Mix well.
Grease and heat a dosa tawa/ griddle.
When it is hot enough, pour 1 laddle of batter to the center of the tawa. Begin to spread from the center and make a thick or thin dosa as per your preference.
Drizzle some oil around the edges. Cook until the edges leave the pan.
Flip and cook on the other side. Flip back and cook until crisp.
Serve millet dosai hot with any chutney.