Take the pieces of rohu fish in a bowl, add 2 tsp of salt and turmeric powder each along with chilli powder and oil.
Mash them with hands and keep aside for 15 minutes to marinate
Now, take garlic, green chillies, mustard seeds, black pepper corns, cumin seeds, whole red chillies and fenugreek seeds in a grinder. Along with it, add a tsp each of turmeric powder and salt along with tomatoes.
Grind all the ingredients together to make a paste.
Now take a pan and put mustard oil in it.
Put the marinated fish in to the pan and fry it well.
Now take the bay leaves and put in the pan along with the grinded paste.
Saute and add ½ a tsp of salt to mix.
Now put the fried fish into the paste. Mix well and add some water.
Let it simmer for 5-10 minutes.
Add garam masala and coriander leaves to the gravy. Stir well. Serve hot.