Firstly, in a large bowl take 3 cup sona rice and methi.
Rinse well and soak in enough water for 4 hours.
In another bowl take 1 cup urad dal.
Rinse well and soak in enough water for 2 hours.
After soaking dal for 2 hours, drain off the water and transfer to the grinder. you can also grind in mixi if you do not have access to a grinder.
Add water as required and blend to smooth paste.
Scrape sides. the smooth and fluffy batter will be ready after 40 minutes.
Transfer the batter to a large vessel and keep aside.
In the same grinder add soaked rice.
Add water slowly and scrape the sides. blend to a coarse paste.
Transfer the rice batter to the same urad dal batter.
Mix well making sure everything is well combined.
Ferment in a warm place for at least 8 hours or until the batter doubles in volume. if you are leaving in a cold climate, then you can place the batter in the warm oven (just heat the oven until it turns slightly warm and then turn off) to ferment.
Once the batter is well fermented, mix gently, without disturbing the air pockets
Transfer 4 cups of fermented batter to a small bowl and add 1 tsp salt.
Mix well until the salt is well combined. masala dosa batter is ready. keep aside
Prepare aloo masala stuffing
Firstly, in a large kadai heat 2 tbsp oil and splutter 1 tsp mustard, 1 tsp urad dal, 1 tsp chana dal, few curry leaves, pinch hing.
Now add 2 chilli and 1 inch ginger. saute well
Also, add 1 onion and saute until onions shrink slightly.
Further, add ¼ tsp turmeric and 1 tsp salt. saute well.
Now add 3 potato and mix well, mash slightly making sure everything is well combined.
Turn off the flame and add 2 tbsp coriander
Now, add a ladleful of batter on hot tawa.
Spread as thin as possible making a crispy dosa.
Take 1 tsp of butter and spread uniformly
Also, place 2 tbsp of prepared aloo masala in the centre.
Roast until the dosa turns golden brown and crisp.
Scrape the sides of dosa and roll the dosa
Finally, masala dosa is ready to serve with sambar.
