Wash and pressure cook the potatoes. Let them cool and then peel and break them into thick pieces with hands. Keep aside.
In a large bowl, add curd and besan with little water and whisk it to make a smooth batter. Make sure there should not be any lumps formed. Keep aside.
Heat oil in a wok and add zeera and hing. As soon as the zeera crackles, add finely chopped onion and saute till onion softens.
Now add finely chopped or minced ginger, garlic and green chilies along with some curry leaves and fry them all together for few minutes.
Now add red chili powder, coriander powder and turmeric and fry the masala well till it starts leaving oil from the sides. If you find the masala sticking the bottom, you can add little water (2 tbsp) in it and fry nicely.
Add the broken potatoes and mix all properly till the fried masala coats the potatoes well.
Now lower the gas flame and start pouring the curd batter slowly and stir gently.
Adjust salt as per your taste and close the lid and let the curry cook for some time.
Once the curry is done, turn off the flames and garnish it with freshly chopped coriander.
Serve hot with chapati, or plain rice.