Cut the salmon fi llet into manageable serving pieces, about 5 x 7 ½ cm. Dust both sides with the salt, cayenne pepper and turmeric and rub into the fish.

Place the fish in a plastic bag and refrigerate for 1-6 hours. Grind 2 ½ tsp of the mustard seeds in a clean coffee grinder or other spice grinder. Put in a bowl. Add the ground coriander, cumin, turmeric, curry powder, cayenne pepper, salt, tomatoes and 120ml water. Mix well and set aside.

Pour the two oils into a large pan and set over a medium-high heat. When the oil is hot, put in the remaining mustard seeds. As soon as they begin to pop, a matter of seconds, add the fennel seeds.

Stir once and put in the curry paste, as well as another 250ml water and the curry leaves. Bring to a simmer. Reduce the heat to low and simmer gently for 10 minutes (the sauce can be refrigerated several hours).

To poach the fish, reheat the sauce in the pan and lay the fi sh pieces in it in a single layer. Simmer on a low heat until the bottom of the fish pieces appear to be done, about 5 minutes. Carefully turn the fish pieces over and cook for a further 4-5 minutes or until the fish is cooked through.