Heat the oil in a kadai or wok over medium heat, until the impurities smoke off and the oil becomes colourless. Remove from the heat and allow the oil to cool before the next step to prevent the spices from burning.
Add the turmeric and chilli powder and cook for one minute, using the residual heat in the oil.
Return to a medium-low heat and add the onions and sprinkle with salt. Cook for ten minutes or until the onions have softened.
Add the ginger and chillies, mix well, and cook for a further two minutes.
Add the curry and fenugreek leaves. Mix well.
Increase the heat to medium and add the fish. Fry for five minutes,gently tossing to cover the fish.
Stir in the coconut milk and bring to a simmer. Cook for five minutes, or until fish is starting to flake and the coconut milk has reduced to a creamy consistency. Add water if needed to maintain this consistency.
to serve
Gently stir in the jaggery and coriander.
Remove from heat, sprinkle with garam masala and serve.
notes
Ling, kingfish or Spanish mackerel or any other firm white fish could be used instead of cod.