Fish in Mustard Gravy

1 kg good fish such as Hilsa or Trout cut into thick slices or wedges
3 tablespoons oil
3 tablespoons yellow mustard seeds
1 teaspoon turmeric powder
8 to 10 green chillies
Salt to taste

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