Smoke the mustard oil in a wok.
Peel and cube the potatoes, smear some salt and shallow fry them. Cook till they are 3/4th done. Then keep aside.
Peel and cut the ridge gourd in semi circles of about half an inch thickness, smear salt and keep aside.
Alongside grind together the soaked poppy seeds (ensure you use very little water, just enough to soak) and green chillies to a thick paste. (You could do this in a mixer or use a sil batta.)
Now to the oil add 1 tsp of nigella seeds/ onion seeds, then add in the ridge gourd pieces. Once the ridge gourd goes limp add the potatoes and the prepared poppy paste.
Next, add a pinch turmeric powder and a little water. Cook till the poppy seed masala coats the veggies well. The gravy should not be too runny, it should just coat the potatoes and ridge gourd well.
Adjust the salt, then add the chopped cilantro. Serve it hot with steamed rice and dal.