In a bowl add idli rice and raw rice. Rinse them once under water and soak in enough water. In another bowl add whole urad dal and fenugreek seeds. Add water for soaking. Rice and dal have to be soaked separately for minimum 6 hours to maximum 10 hours.
After soaking period, rinse rice and dal separately 2 to 3 times once again.
First in a grinder (preferably wet grinder) add urad dal with little water to begin with and grind until it turns smooth and fluffy. This might take somewhere between 30 to 50 minutes based on you grinder and the quantity of the dal used. Add water in very small quantities (about a tablespoon of water each time) in between the grinding time. Also scrap the sides while grinding to ensure all grains of the dal are ground even. One of the key in getting soft idlis is the consistency of urad dal batter. The batter has to be really smooth and fluffy(the volume doubles after grinding)
Once done, remove the dal into a large bowl and set it aside.
Next without washing the grinder, add soaked rice and grind it by adding little water at a time until the rice turns into a smooth batter. Remove into the same pan holding urad dal batter.
With a stainless steel spatula, mix both the batter together. Set it aside for a good 8 to 10 hours for fermentation process. Preferably overnight.
Next day, you will see the batter doubled it’s volume and raised well on top. With a spatula mix it well, add salt to the batter and mix again. That’s it. The perfect idli/dosa batter is ready.
The consistency of the batter for idli will have to be thick to get soft spongy idlis. So do not add water to the batter if you plan to make idlis. And if you want to use this batter for dosas, take a portion of the batter required, add very little water mix and check if you got the right pouring consistency, then use the batter in making dosas.
To make idli in traditional way, I use the aluminum idli pans. And instead of greasing the pan with oil, I use a wet cotton cloth on which I pour the idli batter(thick batter) steam it for 10-12 minutes and then gently remove it from the cloth.
Idli’s made in these traditional idli steamer pans turns out very fluffy, soft and big. Serve steaming hot fluffy idlis with tiffin sambar, coconut chutney, spicy onion-tomato chutney, mint chutney. Or simply serve idlis with idli podi(idli chutney powder) topped with few drops of warm ghee(clarified butter).