Bengali fish curry

Prep time: 5 mins     Cook time: 25 mins     Other: 15 mins
Serves: 4

Delicious fish curry - traditional and spicy (you can adjust the heat as you wish) fish stew. Seasoned with turmeric and ginger, garlic and onion. This curry is very easy to cook at home. Serve with rice. 
My addition of butternut squash is optional.

500 g meaty fish fillets (boneless) - like hake, haddock or halibut
2 tsp salt
1 tsp of turmeric
2 Tbsp vegetable oil 
1 medium onion
1" ginger 
4 garlic cloves
1 Tbsp coriander seeds, toasted and ground
1 tsp cumin seeds, toasted and ground
1 tsp Kashmiri chilli (or to taste)
1/3 butternut squash, cut into 1 cm cubes (optional)
2 Tbsp tomato puree
200 ml canned plum tomatoes
100 ml water
bunch of fresh coriander, chopped
green chillies, chopped (optional)

1. Cut the fish into bite-size pieces. Sprinkle with turmeric and salt and rub into fish. Set aside and let marinate for about 15 mins.
2. Mince ginger, garlic and onion finely together - or blitz in a food processor to make a paste, set aside.
3. Heat the oil in a medium saucepan. Add the fish and cook to sear the fish but do not allow to cook through. Remove and set aside.
4. To the same saucepan, add the garlic, ginger and onion paste. Cook for about 2 mins to soften and dehydrate. If it sticks to the bottom of the saucepan - add a half Tbsp of water. Add the spices (coriander, cumin,  chilli) along with tomatoes, tomato puree and butternut squash (if adding), and water. Cook for about 10-20 mins to reduce the sauce.
5. Return the fish to the saucepan gently to keep the fish in pieces. Lower the heat, cover and allow to cook through, this takes around 2-4 mins.
6. Sprinkle the chopped coriander and green chillies (if adding) and serve immediately with rice.