Ilish aam kasundi / steamed hilsa in mango mustard sauce is an eternal classic recipe of ilish / hilsa.
Gently wash the steaks of hilsa /ilish and pat them dry.
Prepare the mustard paste: soak yellow and black white mustard seeds (10 gm+15gm) in water for half an hour. Drain the water and grind the mustard seeds in mixer with green chillies (3-4 depending upon your taste) to a smooth and creamy paste. Add pinch of salt to it and mix well.
In a bowl add the mustard paste, aam kasundi / mango mustard sauce, turmeric powder and mustard oil, blend it well.
I have used an 1:2 proportion of mustard paste and aam kasundi, you can adjust it according to your taste.
Generously coat the steaks of hilsa / ilish with the mustard-kasundi combo, pour the remaining mix over it, drizzle bit of mustard oil and place 2 green chillies over it.
Close the container tightly and steam it in a steamer for 10-15 minutes.
Serve the aam kasundi flavoured hilsa with steamed rice