Put all the paste ingredients in a mini food processor and blend to a thick paste, adding a splash of water if needed. Heat the oil in a heavy-based saucepan or karahi over a medium heat.

Add the mustard seeds and urid dal and fry for 30 seconds, then add the paste and the turmeric, and fry for 2–3 minutes until fragrant.

Add the water, bring to the boil then add the cod.

Cook for 5 minutes, or until cooked through, occasionally shaking the pan gently to distribute the heat (avoid using a utensil to stir as the fish is delicate and will break up).