Marinate the Rohu fish pieces with less than ½ tbsp of salt and less than ½ tbsp of turmeric powder. Leave it for 10 minutes.
Add 3 tbsp of mustard oil into the wok. Let it heat up. Gently add the marinated fish pieces into the hot oil and let them fry.(Expert tip: Be very careful while adding the fishes into the oil.) Flip them over and fry both sides. Take them out on a plate when they are done.
Now add bay leaf and cumin seeds into the oil. Sauté them.
When they start emitting a good smell, add the chopped onions. Stir the onions until they turn a light brown color.
Add the potatoes and stir them along with the onions.
Add 1 tbsp of salt. Stir it well to mix everything. Add the ginger-garlic paste when the potatoes and onions are fried. Stir it nicely for 2 mins until the raw smell goes away.
Now add the coriander powder, roasted cumin powder, turmeric powder, and red chili powder.
Mix everything very well. Add a little bit of water and then cook; otherwise, the spices will get burnt.
When it is stirred nicely, add the chopped tomatoes. Stir it nicely.
Add 1½ cups of water into the mixture and mix everything. Add green chilis. Now cover it with a lid.(Expert tip: Add water as per your desired gravy consistency. In fact, add salt as per your taste.) When the gravy is boiling, add the fried fish pieces. Let the fish get fully submerged. Now cover it with a lid.(Expert tip: If you want, cut the potato slices as per your choice.) It’s done after a few minutes. Turn off the gas and sprinkle the coriander leaves on top.
Rui Macher Jhol is ready and transfer it hot in a serving bowl. Serve it with steamed white rice.