Marinate the fish with turmeric and salt. Heat mustard oil in frying pan and fry the fish till light brown on both sides. Keep the fish aside.
Marinate potatoes and pointed gourds with turmeric and salt and fry in the same oil till golden brown and tender. Keep aside.
Reheat the same oil, temper it with whole cumin seeds and green chillies. Add the tomato puree, ginger paste, turmeric powder, 2 tsp of the cumin paste, sugar (just a tiny pinch :) ) and salt.
Cook slowly on a moderate flame till oil starts releasing from the masala paste.
Add the fried potatoes and pointed gourds (if at all using) and about 1 1/2 cups of warm water. Give a nice loving stir and bring the curry to a gentle simmer.
Adjust the salt, add the fried fish and cook for a further 5-6 minutes till the gravy thickens slightly.
Serve hot with steamed rice.
