To prepare the batter for Masala Dosa, wash and soak the rice (with fenugreek added into it) and urad dal in separate containers for approximately 6-8 hours. Once the rice and urad dal are soaked well, grind them separately in a mixer using the water in which they were soaked, till the mixture reaches a smooth consistency. Mix the batter of both the ingredients in a bigger container and add salt to it. Combine well and allow it to ferment overnight.

For preparing the filling of the dosa, heat 2 tbsp oil in a thick-bottomed pan and let the mustard seeds splutter. Then, add sliced onions, curry leaves, green chillies and saute them till the onions turn pink. Then, add a pinch of salt and turmeric powder and mix them well.

Now, take the cubed potatoes and add them to the sauteed onions and mix them together. Pour water gradually into the mixture and allow the potatoes to simmer for around 4 minutes. When the mixture is in semi-thick state, turn off the gas and let it rest for a few seconds.

Now, take a dosa tawa and heat it on low-medium flame. Smear 1 tsp oil on it to prepare the dosa. When the tawa is hot, pour and spread the batter of urad dal and rice evenly in a circular motion.

While the colour of dosa's edges turns into brown, reduce the flame and sprinkle few drops of oil on the dosa sides and put 2 tablespoons of filling.