Madras Fish Curry

We were plating up before I thought to take a photo! 

 We've been looking for a good fish curry for years. This one of  Rick Stein's and it is simply delicious. It's his favourite and now it's our favourite fish curry. Thanks Rick!
Ingredients
2 Tbsp vegetable oil
1 Tbsp yellow mustard seeds
1 large onion, finely chopped
3 garlic cloves, crushed
30 fresh curry leaves (from ethnic shops)
2 tsp Kashmiri chilli powder
2 tsp ground coriander
2 tsp turmeric
400 g fresh tomatoes (or 400g can chopped tomatoes)
100ml tamarind water
2 green chilies, each sliced lengthways into 6 pieces, with seeds
1 tsp salt
700g snapper fillets, or other white fish, cut into 5cm chunks
Serve 6

Method
Heat the oil in a heavy-based saucepan over a medium heat. When hot, add the mustard seeds and fry for 30 secs, then stir in the onion and garlic, and fry gently for about 10 mins until softened and lightly golden. Add the curry leaves, chili powder, coriander and turmeric, and fry for 2 mins, then stir in the tomatoes, tamarind water, green chilies and salt. Simmer for about 10 mins until rich and reduced. Add the fish, cook for a further 5 mins or until just cooked through, and serve with plain rice.

Chook’s note:
If making for 2 people, halve the fish quantity but make the full quantity of sauce and freeze half. Then simply thaw it and use with fresh fish or goat or chicken.
If you can’t get fresh curry leaves either leave out or put a tsp of good old Clive of Indian curry powder as a substitute. 
Kashmiri chili powder is very mild so if you don’t have any substitute with 3:1 sweet paprika to cayenne chili powder.  
Rather than bother with starting from scratch with tamarind, buy a small jar of tamarind paste and mix 50-50 with water. Tamarind adds the essential sourness to the dish. Lime or vinegar could be used instead  
The recipe calls for 2 green chilis but if f you don’t like too much heat reduce that amount. 
I have used flake instead of snapper and it worked very well. Just make sure it’s a firm white fish.