Wash the fish pieces well and pat dry them. Apply some salt and half the turmeric and chilli powder to them
Heat about 2 tablespoons of mustard oil until it starts smoking, turn the flame down and fry the fish pieces - a minute on both sides. Drain from the oil and keep aside
In the same oil, fry the potatoes and cauliflower florets until they get a light brown color on them. Drain and set aside
Grind together the onions, two chilis and the garlic to a fine paste. Heat some more oil and add the onion mixture paste, fry this out until the raw smell of the onions goes off
Add salt, turmeric powder, chilli powder and coriander powder, with some water, and cook until oil separates
Now add the potatoes and cauliflower florets and mix well. Add about a cup of water, cover and cook until the veggies are cooked
Now, add the fried fish pieces, tomatoes and two more slit chilis, cover and cook for five more minutes. Turn the flame off, add the roasted cumin powder and coriander leaves
Keep covered for five minutes and serve the fish curry hot with steamed rice and some lime wedges on the side. Enjoy!