Curried fish

Preheat oven to 200 °C.
Cut the fish into smaller pieces and place in a greased ovenproof dish.
Season with salt and add the water.
Sprinkle with the oil, cover with aluminium foil and bake for 30 to 40 minutes, depending on the thickness of the fish, until it's done but still firm.
Bring all the sauce ingredients except the cornflour to the boil.
Simmer until the onions are soft but retain their shape.
Thicken the sauce with the cornflour if necessary.
Arrange the fish in layers in a stainless-steel dish, spooning a generous quantity of sauce over each layer.
End with a layer of sauce.
Chill until needed.
Note:The fish will keep in the fridge for two weeks.