Take clean Hilsa chunks and marinate with ½ Tsp. each of Turmeric Powder, Salt and also 2 Tbsp. Mustard Oil.
Chop 2 Green Chillies, slit 3 green chillies and make a rough paste of the 2 chillies and keep remaining as it is.
Leave the fishes for 15 minutes before cooking.
Now heat 4 Tbsp. Mustard Oil in a pan and lightly fry the fish for 30 seconds on each side and strain from the oil.
This step is very helpful and helps in the non-curdling of milk.
Transfer the oil in a bowl after frying 2-3 green chillies. This oil will be served separately with rice. This is called Ilisher Tel.
Now heat 4 Tbep. Mustard Oil in the same pan.
Sprinkle ½ Tsp. each of Turmeric Powder and salt into the pan having oil.
Temper it with Nigella seed followed by 2-3 whole green chillies.
Now add ginger paste and cook for a minute.
Cook the tempering for 1 minute.
Keep the flame low.
Now add the milk in room temperature.
Add Both chopped and slit green chillies and give a thorough mix.
Add 250ml water as well.
At this point add sugar and adjust salt if needed.
Bring this mixture to a boil and cook till it thickens to ⅔.
Now add lightly fried fish and cook for 5 minutes.
At this point add Green Chili paste/ crusher green chillies and cook for 2 minutes.
Now add 1 Tbsp. Mustard oil and give the curry a mix.
Switch the flame off after one minute of cooking.
Serve it hot with steamed rice.