In a large bowl, add curd, salt and black pepper powder to water chestnut flour and mix well.
Add water as required and whisk into a lump free batter. Keep aside for 15 minutes.
Mash the boiled potatoes and keep aside.
In a pan heat 1 tablespoon oil and add cumin seeds.
Once the seeds crackle, add grated ginger and chopped green chili and stir fry for few seconds.
Next, add turmeric powder and mashed potato. Mix well and stir fry. Add salt and coriander leaves.
Cook for 1-2 minute and put off the flame. Now heat a skillet on medium flame.
Add a ladle full of batter in the center of the skillet. Spread the batter in circular motion.
Drizzle oil on the sides of the dosa. Cover and cook for 2-3 minutes.
Now flip the dosa carefully and cook the other side too.
Flip the dosa again and add potato stuffing to the center.
Fold the dosa and serve hot.
