Step by Step Pictures to Make Idli:

• Wash the rice until the water runs clear. Soak in enough water to cover it by 3 inches and leave aside for 3-4 hours.
• Once the rice has been soaking for 2.5 to 3 hours, wash the urad dal and soak it for 30 mins or so. Amma tells me soaking urad dal for too long is not necessary and it may lose its "potency". Make sure there's enough water for it to absorb and swell - the urad dal requires more water than the rice.
• Wash and prepare your grinder. Add the soaked urad dal...
• and a generous amount of water to get it started. I usually add about 1 cup and see how that goes but this will totally depend on the quality of urad dal you use. My recurrent mistake was always not adding enough water to grind the urad dal.
• It will take about 15 mins for the urad dal to be ground smooth. When you take a little batter and rub between fingers, it should be smooth and flowy. As the urad dal grinds, it will rise and turn fluffy. This is perfect.
• Transfer the urad dal batter to a large enough container and set aside. You don't have to wipe the grinder clean of the batter. When you grind rice, it will automatically get 'cleaner'.
• In goes the soaked rice next.
• Rice doesn't need as much water as the dal so add about 1 to 1.5 cups and see if it gets thick as you grind. When rice grinds, it will absorb the water so test in between and keep adding water as you go, a little at a time. Grind rice to a smooth pate too and this takes me around 25 mins or so in my grinder.
• Once done, add this to the urad dal batter and top off with some salt. Mix gently so that the rice and dal get combined well.
• The consistency should be fluffy and the batter should fall down easily from your spoon as you mix it.
• Set aside this batter in a container that is only filled halfway with the batter to allow room for rising during fermentation.
• The urad dal would have risen to the top leaving the heavier rice batter at the bottom so you need to mix it uniformly before making idlis.
• Pour into greased (I use gingelly oil or Indian sesame oil) idli moulds and steam for 10-12 mins for super soft and spongy idlis.