Fish in Mustard Gravy

1 kg good fish such as Hilsa or Trout
3 tablespoons oil
2 tablespoons mustard powder
1 teaspoon turmeric powder
8 to 10 green chillies
Salt to taste

Make a paste of the mustard with about 6 tablespoons of water. Heat oil in a non-stick pan and fry the mustard paste and turmeric powder for about 5 minutes on low heat. Add 3 cups of warm water and mix well. Bring to boil. Add the fish, green chillies and salt and cook on medium heat till the fish is cooked and the gravy thickens a bit.