Wash and soak separately the idli rice and the udad Dal for about 20 hours. Methi can be soaked together with udad Dal.

Cook the par boiled rice as normal and keep them ready before grinding the batter. That's how it looks (pic 2) after cooking.

Grind udad Dal and methi to very smooth batter. Add only a little water at a time as needed for grinding. USE WARM WATER IN WINTER. If your grinder is making abnormal noises (like it's hard for it to run) or gives jerks, understand that the batter is too thick to be grinded and hence you need to add a little bit water. But if you add more water than required, it won't grind smooth enough.

When the batter feels smooth enough, take it out in a big container that has a tight lid.

Grind the idli rice and the cooked rice together till very smooth batter by adding only a little water at a time as needed for grinding. This batter in particular does not feel as smooth as the Dal batter. Still try to get it as smooth as possible. The grainy texture should be only 5-10 %.

Mix the rice and the udad Dal batter along with salt. Beat it well using your hands/whisk for about 5-10 min. Keep it for fermentation in a warm place. It may take between 12-24 hours for the batter to rise, depending on the climate. (Once it took 48 hours to rise! The idlee texture & smell were usual, but idlee tasted a bit sour) You may wrap the vassel with a blanket and place it in a warm oven to speed up fermentation. The batter gets light and frothy (pic 2 and 3) when fermented well.

The batter can be refrigerated for 4-5 days. As the batter gets used up and stays longer, it looses the air bubbles and hence gets harden a bit. Such batter is not ideal for idlee, but you can use it to make dhosa. If you freeze the batter, it can stay upto 2-4 weeks. Whether refrigerated or frozen, it has to be brought down to room temperature before use.

If you have made extra batter for later use, it is advisable to take out required quantity without disturbing the air bubbles in the rest of the batter. Handle and move the remaining batter very gently so as to keep the air bubbles intact.

This batter is so perfect (when fresh) that there is no need to add soda or eno while cooking idli, not even a pinch. Yet the idlis will be soft and smooth like a sponge.
However, if the batter is not airy enough, you may want to add eno.

Try to control the fermentation period right from the beginning. Find out what leads to faster fermentation - putting in the oven or wrapping in the blanket and put in the sunlight. Prolonged period of fermentation makes idlee/dhosa sour.

What can you make with it?
1. Idli

2. Dhosa

3. Yalappa

4. Uttapam
Just replace rava batter with this batter.

5. Soft dhosa

If someone is not allowed to consume udad Dal, here is what you can replace with.