Take everything except the salt in a bowl. We are using the Urad that is whole and is not husked.
Fill it with water until comfortably covers them, overnight. The below picture is from the next day morning where it has soaked up much of the water.
Add all this together to a wet grinder. You can use a mixie/ processor but personally a wet grinder is just perfect for dosas and idlis.
As mentioned earlier in the post, the black gram was not soaked traditionally and just ground into flour first. It was set aside and the rice was ground into a batter. Then the flour was added. But I prefer soaking my whole foods first and hence this method of soaking them all and then grinding them together appeals to me.
I use the soaking water to grind the water.
You might need more or less, enough to make a smooth batter that's thick with buttermilk consistency.
Pour this into a big vessel which provides height for the batter to rise up while fermenting.
and give it a good mix. I personally prefer using hands (traditionally used as well) where the belief is that the body heat aids in the fermentation process.
Set aside in a warm place covered with a lid (not air tight).
Depending on your region and humidity level, it might roughly take anywhere between 6-24 hours.
See how it has risen and almost doubled? That's a well fermented batter. This would provide a wonderfully porous dosa.
Mix it well and then store in a air tight vessel of your choice in a refrigerator. Bring it to room temperature when ready to make the dosas. I love using a cast iron skillet for dosas and keep one specially for making them. Heat a pan well until it sizzles when drops of water is added to the pan. Lower the heat and lightly grease the pan with sesame oil (traditionally used) using a paper towel or a half cut onion. But you can use any oil of your choice. Pour a ladle of batter
and quickly spread it in a circular motion to the desired thickness. Increase the heat back to med-high. A thick spread would make for a soft pillowy dosa.
You can drizzle few drops of oil if you like around the dosa. Wait for few minutes or until the bottom gets browned and you are able to easily lift the sides with a spatula.
Turn the other sides and cook for another couple of minutes, or until done.
Here, I have spread the batter thin, almost like a crepe. This makes for a crispy dosa and is mostly preferred in our house.
Turn the other side for few seconds and remove to a plate. While making thin dosa, cooking just one side is mostly enough.