Bengalis and fish curry is an abiding love affair.  Macher jhol or fish curry ranks right on top in Bengali cuisine. Fish curry and rice is the staple diet for almost all Bengalis, and there are as many varieties of fish curries as there are fish. One such delicacy is Rohu or Katla Maacher Kalia. It occupies a place of pride in the Bengali  cuisine repertoire. The curry is made with either Rohu (known as Rui in Bengali) or Katla, both freshwater fish, in a spicy and rich gravy of tomatoes and yoghurt, flavoured with caramelized onion, garlic and ginger paste, green chilies, garam masala, and even raisins. This flavoursome fish curry is served at special occasions, especially weddings, but it can be made for any meal and is deliciously satisfying. 

It is said that Rui or Katla Maacher Kalia has its origins in Mughlai cuisine, and  However, the dish, popular during the rule of the Bengal Nawabs, has been adapted over the years.

Below is a detailed recipe of Katlar Kalia (you can alternatively use Rohu)

Ingredients 

1 whole, large Rohu/Katla fish

2 tablespoons mustard oil

2 to 3 teaspoons of turmeric powder

4 big onions

1 ginger

3 tomatoes 

5-6 green chilis

I small pot of yoghurt

1 teaspoon cumin powder

1 teaspoon red chili powder

1 teaspoon Kashmiri red chili powder

5-6 raisins

4 dried red chilies

4-5 bay leaves

1 teaspoon ghee

1 teaspoon cumin seeds

4 cardamom pods

2 pieces of cinnamon

4 pieces of cloves

1 teaspoon sugar

Method

. Cut the fish (preferably get it cut at the market) and wash properly

. Marinate the fish with salt and turmeric and keep aside for 20 minutes

. Peel the onions, cut one onion in thin slices and the other 3 into medium-sized pieces

. Peel and chop the ginger

. Take the medium-sized onions and ginger, grind together, and make a paste out of it

. Deep fry the sliced onions in mustard oil until it turns golden brown, and keep aside

. Put the curd in a bowl and whisk

. In a small bowl, put 1 teaspoon turmeric powder, 1 teaspoon cumin powder, 1 teaspoon red chili powder, and 1 teaspoon Kashmiri red chili powder

. In the same oil in which the sliced onions were browned, place each fish piece into the oil

. Deep fry the fish, on both sides, on high heat until it turns golden brown

. Take off fire and keep aside

. In the same oil in which the fish was fried, put some ghee, the dry red chillis, bay leaves, cardamom, cinnamon, cloves, and cumin seeds and fry

. Then add the ginger-garlic paste to the above mixture and cook for 5 minutes, till the oil comes up

. Add the turmeric powder, cumin seeds, red chilli powder, and Kashmiri red chili powder, mix and fry well

. Add water to the pan, and mix the above paste well. Add salt as per taste preference

. Add about 1 teaspoon sugar and mix well

. Add the chopped tomatoes and 4 slit green chilis

. Put a lid on the pan and let it simmer for 5 minutes

. Add the whisked curd, and mix

. Wait till the oil rises, then add 1 or 2 sliced green chilis and raisins, mix well

. Add 3 cups of water and allow it to boil

. Place the fried fish, fried sliced onions and 1 green chilis, mix well. Add garam masala

. Cover the pan and wait till it cook for 5 minutes

Rohu or Katla Maacher Kalia is best savoured with steaming Basmati rice.