For preparing Kerala Style Masala Dosa, first soak the ingredients in water for about 2 to 3 hrs.
Grind it in a blender adding water in steps into a very fine batter.
Add salt and keep it overnight for fermentation.
Heat oil in a pan or a kadai.
Splutter mustard seeds .
Add onion and saute till it turns brown.
Add ginger-garlic paste and saute again.
Add slit green chillies, turmeric powder, tomatoes and continue to saute.
Add mashed potatoes followed by water and salt.
Cook, till it becomes thick.
Add chopped coriander leaves and keep it aside.
For masala dosa:-
Heat up a dosa tawa.
Pour a ladle of dosa batter on the tawa and spread it thin.
Pour oil or ghee over it.
When one side is cooked, place a portion of the masala in the center and cover it with the other half of the dosa.
:- You need not turn the dosa to cook both the sides.
:- Serve Masala Dosa hot with Sambar and Chutney.