For stuffing soak dal for at least 3 hours, drain the water.
Grind all the stuffing mix except potato in a grinder to make coarse paste, do not use any water I like to use food processer. Stuffing should be moist. Add potatoes and mix it well, Set aside.
Mix sooji, salt, and yogurt, add water as needed to make a pancake-like batter. Set aside for at least 30 minutes.
To make stuffed idli, grease the idly plate. Add Eno Fruit Salt to the batter and mix well. The mixture will begin foaming. Immediately begin pouring into the Idli trays.
pour about 1 tablespoon of batter and spread evenly. Now add 2 teaspoons of masala and pour over about one tablespoon idly batter covering the filling. Repeat the process. Place the stand into the steaming pot.
Cover the pot and steam idles for about 12 minutes on medium heat. Insert a fork in the center of one idli. If the fork comes out clean, remove the stand from the pot. Do not overcook idles, as they will lose their softness and dry out as they cool.
Cool for just a few minutes before removing each individual idli. They should come out easily and not stick to the mold. Idles should be spongy and soft.