Heres a recipe for really quick idli.
1 cup sooji (rawa/ wheat germ)
1+ cup sour curd (u can keep it out of the refrigerator overnight)
1/2 sachet Eno
1/4 tsp salt
Mix the curd with sooji and salt. Vary the quantity of curd so that the batter is neither too thick nor too runny. It shud resemble the consistency of pancakes batter.
Also add salt. Keep this for abt 15-20 mins. Just when u r ready to cook the idlis - add eno. Mix it quickly - but dont over beat the batter. Pour this into the idli moulds and microwave it for 5 minutes. (make sure that the moulds are just a bit more than half full - idlis need space to become fluffy) (dont forget to add water to the base of the mould)
After 5 mins - cool the idlis a bit - and take off the moulds - they'll just slide off easily - hot idlis - ready to eat with sambhar/ chutney etc.