Method

1. Wash both types of  rice two to three times and soak them  in a broad vessel , for  four to five  hours.
2.  Wash the dal too , two to three times and soak separately adding fenugreek seeds , for four to five hours.
3. Take a wet grinder , and grind the dal to a smooth batter adding sufficient amount of water
4. Take water to grind  ( 1 cups  or a little more) . Add half cup water before grinding, add the dal and grind .
5. While the dal grinds , add rest of  the water
6. The dal increases in volume and becomes smooth and spongy , and gurgles as it grinds .
7. Remove the batter from the grinder and transfer to a vessel.
8. Now add soaked rice and grind to a smooth batter adding sufficient amount of water .
9. Mix both the batter and add salt . Mix well  with your hand or ladle .
10. Keep  aside to ferment for  8 hours in hot climates  . In colder climates, the batter may need more time, like say 12 to  24 hours.
11. The batter would have risen during fermentation, so keep in a bigger vessel to prevent the batter from spilling out .
12. Only if the batter is well fermented the idlis will come out nice and fluffy.
13. Refrigerate and use.

Note

• The Idly batter is thicker than dosai batter , so make sure that the batter is not too watery while making the batter . Add water judiciously.
• The black gram dal or urad dal ‘s quality should be good to get a good spongy idli .
• if you want the batter only for idly , grind the rice a little coarser .
• If you are grinding the batter in mixie , take rice and dal ratio in  2 : 1 proportion as the batter wont be aerated well in the mixie.