Wash thoroughly Green gram dal when washing the husks tend to come up you can throw if you wish to or save them up, some might escape but wash and soak them
Wash the millets throughly with the urad dal and fenugreek seeds.
Soak all the above ingredients at least for 4 to 5 hours, even though Green gram and urad dal doesn't need long time to soak.
Grind them all together in a mixie or table top wet grinder to smooth batter consistency using water as needed
Once done leave it covered in a warm place for it to ferment preferably overnight for 7 to 8 hours depending on the place you live.
Once Fermented use the batter to make Idli and if you plan to make dosa take some batter in an other container and thin it down to Dosa batter consistency!
Enjoy and make crispy dosas or Idlis.