Boil the potatoes to soft. Once done, let it cool, then peel, mash and keep that aside. Just make sure there are no chunks.
In a bowl, take the rice flour, curds, green chillies, coriander leaves and salt. Mix well. Then add the mashed potatoes and sufficient water to achieve a dosa like consistency. Mix well to ensure no lumps are formed.
Heat a tawa, add some oil and once the pan is hot, pour a ladleful of batter in the center and spread like the regular dosa and wait till its cooked well. Then flip to the other side and cook its done.
Serve hot with chutney.