Wash the Idli Rice, Urad , Dal, and Methi Seeds, and Soak for 3- 4 hours like how we soak for ordinary Idli. After that with a mixer or Grinder grind the Soaked Idli Rice, Urad dal, and Methi Seeds separately by adding the required water.
Now to the ground batter add in the Ragi flour and mix well. Add water little by little and bring to the right consistency which should be similar to the Ordinary Idli batter.
Now transfer the batter to a bog vessel and allow it to ferment overnight. The next morning the batter would have raised up so use a big vessel otherwise it might overflow and become messy.
With the help of a ladle mix the fermented batter well and add salt and mix well. Add water if you feel the batter is too thick. Now grease the idly plate with oil and pour the batter.
Allow it to steam cook for 10-12 mins in an Idli pot. Once cooked switch off the flame and allow it to cool down for 5- 10 mins and then remove the plate from the steamer and sprinkle little water on top of the idli and remove it using a spoon and serve hot.
Notes
The same batter can be used to prepare Dosa as well, however, we need to dilute is a bit more for Dosa.