In a bowl take rice & urad daal wash them together & add 1.5 cups water & soak them for 5-6 hours.

After 5-6 hours drain the excess water & take the rice & dal in a mixture grinder, add water & curd & make a smooth paste like batter.

Remove everything in a big bowl add salt mix well cover it & let it ferment for 8-9 hours.

You will see that the batter has doubled in quantity & small air bubbles have formed, mix it once nicely, then spread the batter on a hot tawa add butter & make dosas out of it.