Wash rice and quinoa thoroughly and combine them. Add 4 cups of water and soak them for at least 6 hours.
Wash Urad Dal and soak it in 2 cups of water for at least 4 hours.
Grind the soaked grains and lentils till you get a smooth batter. Add water, if needed to get a flowing batter ( not too thin, though).
Whisk the batter for a few minutes. Then cover and let it ferment overnight in a warm place.
The next day, add salt and besan (gram flour) and mix the batter. Add water if the batter is very thick. For perfect dosas, the batter should have a flowy consistency and shouldn't be too thick.
Heat a pan. Grease it. On medium heat, spread the dosa batter using a ladle. Spread it as thin as possible.
Drizzle some oil/ghee and let it cook on medium heat until you see it browning.
If you have spread the batter thin, you don't need to turn it. If you see that the surface of the dosa on top looks a bit raw, turn it for a few seconds and take out the dosa.
Serve hot with any chutney of your choice.