Peel the potatoes. Using a fork prick them all over. Heat mustard oil and deep fry on slow heat till about half done. Remove and cool. Again using a fork prick them all over and put them back in hot oil. Cook till potatoes are completely done. Remove and keep aside.
Separately whisk together curd, saunf powder, saunter powder, black cardamom, cinnamon, shahi jeera, hing and kashmiri chilli powder. In a vessel heat mustard oil and add the whisked curd. Increase the heat and keep stirring till the curd gets a boil. Once it boils lower the heat and let it cook for 5 minutes. Now drop the potatoes with a dash of water and some salt. Cover and cook till oil floats on the surface. Serve hot.