Mix salt to ash gourd. It will release water.
Marinate the fish heads with salt and turmeric powder.
Heat the wok (Kadai) and add mustard oil in it.
Fry the heads in mustard oil.
Take them out on a plate.
Fry the potato slices in same oil. Add some salt & turmeric into it.
Take out the shallow-fried potatoes on the same plate.
Add oil in the kadai.
Strain water from ash gourd. Add it to oil. Add black cumin. Give it a good stir. Mix well.
Add ginger garlic paste into it.
Stir for 2 minutes.
Add all the spices.
Stir fry everything very well.
Add some water into it.
Again, add some salt into it.
Add fish heads & potatoes in it. Mix well.
Add 1 cup of water.
Add green chillies.
Cover the pan with a lid. Let the hilsa head with ash gourd boil on medium heat.
Check if water has dried.
Sprinkle roasted masala and mix well.
Break the fish heads into 2-3 pieces and mix well with the dish.
Pour Hilsa head with ash gourd on a plate. Serve it with steamed rice.