1. Wash Bhetki fish chunks and rub Lemon Juice and half of the salt to fish pieces and leave those for 1 hour.
2. Make a thick paste of both types of Mustard Seeds by adding a little salt.
3. Strain the paste through a strainer and discard the husk.
4. Now make a paste of Green Chilies.
5. In a bowl take Mustard Paste, grated Coconut, Green Chili paste, salt, Turmeric Powder, and Mustard Oil as well.
6. Mix those using a spoon.

Marination

1. Marinade fish chunks with this paste and give those an overnight stand (5-6 hours). This step is important to get super soft Paturi.

Making of the Fish Parcel or Macher Paturi:

1. Take the bowl full of marinated fish out of the refrigerator for at least one hour before cooking.
2. Take Banana Leaf and cut it into 6”/6” pieces.
3. Now brush little Mustard Oil on the glossy side of the Banana Leaf pieces.
4. Lightly roast those over low flame for 30 seconds.
5. Now take a piece of Banana Leaf and put 1 spoonful of the marinade on the middle of the leaf.
6. Place a fish chunk on the top of the marinade and finally put some marinade to cover the fish from the top.
7. 
8. Close the Banana Leaf from four sides to make a close parcel.
9. Tie it using a thread as shown in the picture.
10. In case the thread is not available or you find this process a bit fussy then just close it using a toothpick.
11. Following the process make a parcel of the rest of the fish chunks.
12. I was not available with sufficient banana leaves and used a guard leaf to make the parcel for a few pieces.
13. Now put some Mustard Oil in a flat pan and place fish parcels over the oil and cover the pan with a lid and cook on low flame for 10 minutes.
    
14. Flip all the fish parcels after 10 minutes and cook from the other side by covering the pan with a lid for 10 more minutes.
15. Take all the Fish Parcels or Bhetki Macher Paturi and store those in a closed container to enable those to get cooked in their own heat.