In a large bowl, soak 1 cup urad dal, ½ cup chana dal, ½ cup toor dal and 1 tbsp Methi seeds. Keep them aside for 30 minutes. Also, soak poha in a separate bowl.
Add daals and poha to the blender and make a smooth paste. Take the batter from the blender and then blend a coarse paste of overnight-soaked rice.
Now, mix both the batters together. Make sure everything is well combined. Let the batter ferment for 8-10 hours.
To prepare the filling, heat some oil in a pan. Add mustard seeds, cumin seeds, urad dal, chana dal, dry red chilli, curry leaves and saute.
Now, add some onion, ginger, turmeric, salt and saute again for a while.
Mix boiled potatoes with the spices and mash them a little. Turn off the heat and add coriander and lemon juice to the yummy potato filling.
Finally, heat the non-stick pan over medium flame and pour a little oil over it. Rub it all over the pan with a half-cut onion.
Pour a ladle full of batter into the centre of the pan.
Spread uniformly all over the pan in a clockwise direction and in a circular motion.
Now, spread 1 tbsp of butter all over the dosa batter. Flip it over to cook on the other side. Place the masaledar potato filling at the centre.
Close the dosa and cook it until brown.
Serve the crispy, yummy Masala Dosa with coconut chutney and sambar.