Panch phoron diye macher jhol (Fish Broth using Bengali five spices)

I had this at Sujaya di's place some months ago. When Summer came, I started craving for something light and nourishing. If you have access to freshly -caught fish(one of our friend's supply us with his catch of the day sometimes. Joy da , I am talking about you :) ) you can use this recipe with great jubilation. Sometimes, I even use frozen Tilapia fillets and it tastes as good.

পাঁচ ফোড়ন  দিয়ে মাছের ঝোল 

1. Steam the frozen fillets for a minute in microwave(Skip this step if you are using fresh fish)
2. Dry excess water with paper towels. Cut the fillets into halves. Rub on both sides evenly: freshly squeezed lime juice, turmeric, salt, red chili powder, bhaja masala(dry roasted cumin-coriander, ground to powder). Keep aside.
3. In a wok, add mustard oil and shallow fry the fish. Remove and drain in paper towels
4. In the same oiil, you used for frying, add 1 tsp panch phoron (equal parts fenugreek seed, nigella seed, cumin seed, black mustard seed and fennel seed), minced onions, minced garlic, minced ginger and minced green chilies.  Sometimes, I slip a few extra methi or fenugreek seeds because I like its flavor in fish broth.
5. Add potatoes (steam in a microwave to save cooking time). When the potatoes are about done, add diced tomatoes. After sauteing for a while (Bengali : কসানো ), add lukewarm water (1 cup , 1 min in microwave). Cook covered. 
6. Add the fish and turn at the most once. Add chopped cilantro when it is about done. Kill the flame. Serve with steamed rice.

You may use salmon fillet for this light broth. Temper it with kalo jeere and methi instead of panch phoron.