Marinate the hilsa heads with salt and turmeric powder and keep aside for 15-20 minutes.
Pour oil into the wok.
Slide the hilsa heads one by one into the smoking oil.
After the heads are fried, take them out on a plate.
Fry potatoes and pumpkin in the same pan. Add some salt to the vegetables and continue stirring.
Take out the half-fried vegetables on a separate plate.
Add eggplants to the oil. Sprinkle some salt and turmeric powder.
Take out the lightly fried eggplants on a plate.
Add radish and stir for a few minutes before taking them out on the plate.
Add some oil to the wok.
Add bay leaf, dry chilis and panch phoran.
When they start spluttering, add Malabar spinach stems and sliced onions and cook till they turn light brown. Add some salt. Mix well.
After a few minutes, add ginger-garlic-chili paste and give it a good stir.
Add turmeric powder, coriander powder and red chili powder. Mix well. Add some water so that the spices are not overcooked.
Add all the lightly fried vegetables and give it a good stir.
Cover the wok with a lid.
When the vegetables are half done, add the fried hilsa heads, water and some salt.
Spread the Malabar spinach over the curry in a layer. Spinach will release water and will get cooked in its own juice. Let it cook for a few minutes. (Make sure to add spinach later as doing so will help retain its colour.)
Cover it with the lid. Let it cook for sometimes. Open the lid and stir lightly.
Ilish Macher Matha Diye Pui Shak is ready and transfer it to a bowl. Serve it hot along with plain steamed rice.