1. Grind the Urad dal to a smooth paste using a blender;
2. Add enough water to make a fine paste, but also keep in mind not to make it too watery.
3. Blend well, for at least 5-7 minutes.... Fluffier the batter, the better!
4. Add rice to the blender and grind further with some water.
5. Pour into a separate container and ferment overnight or, for about 8-9 hours;
6. Make sure the container has enough room for the batter to rise.
7. Add salt to the fermented batter and mix well;
8. Smear a couple of drops of oil on each depression of the idli stand and pour 2-3 spoons of the batter into each one of them.
9. Steam cook the idlis in a pressure cooker for about 14-15 minutes; Make sure you remove the weight.
10. Remove stand from cooker and let cool for a minute or two;
11. Use the back of a spoon or a knife to remove the idlis;
12. Relish hot with coconut chutney or sambhar or any other gravy of your choice.

Tip:

1. If your feel the batter isn't fermenting well, you could try placing it in a warm place, like, the MW or inside the conventional oven.
2. You could even use idli rava instead of sona masoori rice, to give a different texture to your idlis.

Note:
Made of lentils and rice, this light food is very low in calories

Courtesy: http://maneadige.blogspot.com/