Stein's Fish Curry

I couldn't resist making note of this curry on our flight back from Europe. Rick Stein has put a lot of research into curries, so I trust that this would be a good starting point from which to dabble in this a bit more.

4 tblsp vegetable oil
1 tblsp yellow mustard seeds
1 large onion, finely chopped
3 garlic cloves, finely crushed
30 fresh curry leaves
2 tsp Kashmiri chilli powder
2 tsp ground coriander
2 tsp ground turmeric
400 gr chopped tomatoes
100 ml tamarind liquid
2 green chillies, sliced lengthways into 6 pieces
1 tsp salt
700 gr snapper fillets, cut into 5 cm chunks
boiled basmati rice

1.  heat oil over medium heat, when hot add mustard seeds and fry for 30 seconds
2. stir in onion and garlic and fry gently for 10 minutes
3. add curry leaves, chilli powder, coriander and turmeric and fry 2 minutes
4. stir in tomatoes, tamarind liquid, green chillies and salt, simmer for 10 minutes or until rich and reduced
5. add the fish, cook for a further 5 minutes or until just cooked through
6. serve with plain rice