Take a pressure cooker and heat oil in it.
Temper the oil with Hing, Green Chilies and Kalonji. Once it starts spluttering, add the potato cubes.
Stir it once and season it with some salt as per your taste.
Add the water and put on the lid of the pressure cooker. Allow it to whistle for once and then turn off the heat and let the steam disperse on its own.
Then open the cooker and check if the potatoes are done. Also, check the consistency of the gravy as per your need.
Serve with luchi.