1Clean and cut the Katla fish into pieces. Marinate with a pinch of turmeric powder and salt. Set aside for 15 minutes.
Heat 2 tablespoons of mustard oil in a pan. Fry the marinated fish pieces until golden brown. Remove and set aside.
In the same pan, add the remaining mustard oil. Add finely chopped onions and sauté until golden brown.
Add ginger paste, garlic paste, and green chilies. Sauté for a couple of minutes until the raw smell disappears.
Add chopped tomatoes and cook until they become soft and the oil starts to separate.
Add turmeric powder, cumin powder, coriander powder, and red chili powder. Mix well and cook for another 2-3 minutes.
Add 1 cup of water and bring the mixture to a boil. Add salt to taste.
Gently add the fried fish pieces to the curry. Cover and cook on low heat for 10-15 minutes.
Sprinkle garam masala and mix gently. Cook for another 2 minutes.
Garnish with fresh coriander leaves and serve hot with steamed rice.