Make mustard paste Soak both mustards + posto in warm water for 15 mins. Drain and grind to a smooth paste with 2 green chilies and a pinch of salt. _Tip: Add salt while grinding to cut bitterness._
Rub ilish pieces gently with 1/2 tsp turmeric and salt. In a steel tiffin box or microwave-safe bowl with lid, mix mustard paste, curd, coconut if using, 2 tbsp raw mustard oil, remaining turmeric, and salt. Coat fish pieces well in this mix.
Place slit green chilies over the fish. Drizzle 1-2 tbsp more raw mustard oil on top. This oil is key for authentic flavor.
Seal the tiffin box tightly. Steam in a large kadhai/deep pan with 2 inches boiling water for 12-15 mins on medium heat. Or pressure cook without weight for 10 mins. Or microwave covered for 6-7 mins.
Let it sit 5 mins before opening. The aroma will tell you it’s done.
Serve with gorom vat
