Soak Rice and Uzhunnu overnight or minimum 4 hours
Grind Uzhunnu with a little water, don't add too much water but just enough to grind the dough. This has to be ground to very smooth creamy consistency.
Pour it into a container
Grind Rice with very little water, just enough for it to grind. Towards the end, add boiled rice and salt. This does not need to be ground really well like uzhunnu. A rough texture is good.
Mix this into the dough of Uzhunnu,mix everything together and keep it overnight. In cold Countries, you can warm the oven for few minutes and keep the container inside the over. By morning, the dough will rise up a little bit and you will have a sour smell.
Stir it nicely, check the salt and consistency of dough. For idly dough, keep the consistency thick. Pour them into idly thattu.Once you close the lid of Idli thattu, keep it on high flame and cook for 10 minutes. then couple more minutes on low flame and check with a fork if its cooked. Serve warm and enjoy!