Wash rice, dal and poha separately and soak them separately. Rice should soak for a minimum of 4-5 hours. Dal and poha for about on 2-3 hours.
After the said time, drain the excess water from dal. Add it to the grinder and grind it to a fine batter with water. I use wet grinder for grinding idly-dosa batter.
A well ground urad dal batter fluffs well in the grinder and makes a 'cluck, cluck' sound while grinding, because of the air incorporated into the batter while grinding.
Transfer the ground urad dal batter to a clean vessel.
Next drain the excess water from rice and it along with poha to the grinder and grind it to a fine batter.
While the rice is 3/4th done, add the cooked rice to it and grind to a smooth batter.
Once the rice is ground well to a smooth batter, add the urad dal batter to the grinder, grind for another 5 minutes for both the batters to mix well and then transfer the entire batter to a clean bowl.
If you prefer to mix them well with your hands, then transfer the ground rice batter to the urad dal batter and mix it well.
Make sure the vessel in which you transfer the ground batter is large enough to hold the fermented batter too.
Mix the batter well and leave it on the kitchen counter to fermenthe for about 8-10 hours.