Making idlis successfully is more of an art than a science. You can do everything right, and still have a batter that refuses to ferment and/or rise. It depends a lot on the weather, the temperature, the quality of the rice and the lentils. The batter could ferment, but you could end up with hard, rock like idlis if it does not rise.
But with the above method, I have been getting consistently soft and fluffy idlis.
Products That Have Worked For Me:
I use Laxmi brand idli rice, and Laxmi brand whole, skinned urad. But any good quality rice and lentil should work.
This in no way means I am endorsing these products, just sharing what has worked for me.
1. It's important to let the urad grind really smooth to a buttery texture and give it enough water to make it airy.
2. The final batter should not be too thick - it needs to be only slightly thicker than pancake batter. This allows the air bubbles to form.
3. It needs to be allowed to ferment in a warm area. I typically keep it in a sunny spot in my lanai. It helps the bacteria that aid fermentation to form quickly.
It's a bit temperamental, but when you see that fermented and doubled batter, it makes you so happy!
4. I use a pressure pan to make my idlis, and find it's enough. You may use any wide, deep stainless steel pot to cook them - any 5 quart pan would work well. There are special idli pots sold in India, but I have never used them. They just need a covered pot to steam in.
5. If the batter has fermented but not risen, you will end up with flat idlis
6. The proportion and quality of the ingredients is important. If the urad is too much, you will end up with flat idlis that have a strong urad flavor
7. I have discovered that adding the poha to the soaked rice for about 10-15 minutes makes the fermenting a sure thing, and also yields super soft idlis. Try not to skip it!
Happy idli making!