Rinse idli rice, toor dal and urad dal together well. Then soak 1 cup idli rice, 1/2 cup toor dal, 1 tablespoon urad dal, 3 red chillies in water for 4 hours.
If using small chillies add 6 chillies, I used the long variety so added only 3. You can soak then rinse too.
It should be soaked well.
Transfer this to a mixer jar along with chillies with a 1 inch ginger piece along with water.
Add water little by little to make a runny batter.
The batter should be very runny so add water later after grinding too.
Heat 2 teaspoon oil add 1/2 teaspoon mustard seeds, let it splutter. Add 1/2 teaspoon cumin seeds let it splutter then add 2 tablespoon curry leaves chopped and a pinch of hing.
Add 1 cup finely chopped onion along with salt saute until onions turn transparent.
Cool down completely then add it to batter.
Mix it well.
Add mixie rinsed water and little more water.
Mix well to form a runny batter like rava dosa batter. Add salt if needed.
Heat dosa tawa : Take a laddle full of batter, drizzle it in circular motion.
Fill in the gaps.The tawa should be hot only then holes will form while pouring the batter. Add more water if the batter is too thick.
Drizzle oil at the edges and inside.
Let it cook in medium flame until golden.
Flip over the dosa and cook till golden.
Fold and serve hot! Repeat to finish the batter.
Crispy toor dal dosa is ready!