Heat 3 tablespoon mustard oil in a heavy-bottomed pan.
Once hot, add the potatoes and fry for about 2 minutes. You don't need to deep fry them.
Add salt at this point.
Then, add the onions and ridge gourd and continue frying on low heat for approximately 7 minutes, or until the potatoes are about two-thirds cooked.
Add the sliced green chilies, followed by 2 cups of water.
Cook for another 5 minutes on low heat. By this time, the vegetables should be perfectly cooked but still maintain their shape.
Now add the poppy seed paste aka posto bata.
Mix everything well and cook for about 2 minutes. Once the curry has reached your desired thickness—I like mine a bit runny—add a tablespoon of mustard oil and stir it in. If you prefer a drier curry, simply cook it a little longer.
Turn off the heat and let the curry sit for 15 minutes before serving.