1. Soak the gram dal in 1 cup of water and drain.
2. Mix the curd with about half cup of water.
3. Lightly roast the semolina in a heavy bottomed vessel on a low flame stirring continuously. Cool.
4. Heat the oil in a pan and add the mustard seeds.
5. When they begin to splutter add the chopped green chilies, curry leaves and gram dal.
6. Fry for 5 minutes. Cool completely.
7. Add this mixture to the roasted semolina.
8. Blend with the beaten curd and mix well to make a slightly thick batter.
9. Leave this to ferment for about 6 to 7 hours.
10. An hour before steaming the idlis, add the cooking soda.
11. Add salt when just about to make the idlis.
12. Serve with coconut chutney.

To Steam the Idlis:

1. Grease the idli moulds well with oil.
2. Put a ladle full of batter into each mould.
3. Heat about 1 to 1 ½ glasses of water in a big vessel.
4. When the water starts to boil, put the idlis to steam.
5. They should be one in about 10 minutes.
6. Insert a knife to check whether done.
7. If the knife comes out clean, the idlis are ready.