Doi Ilish (Yoghurt Hilsa Curry)

Ingredients: 1. Hilsa (ilish) – 800 gms (cut into ½ inch thick pieces). 2. Mustard oil – 1 cup. 3. Onion – 3 medium sized. 4. Salt to taste. 5. Coriander Powder – 1 tbsp. 6. Red Chilli Powder – ½ tspn. 7. Mustard paste – 1 tbsp. 8. Green…