Cook the onion gently in the butter for a few minutes, then add the rice.
Continue cooking gently and stirring, adding the curry powder and nutmeg. After a few minutes, add the milk, cream and 250ml/9fl oz water.
When the mixture begins to simmer, add the fish and continue simmering, stirring occasionally until the rice is cooked. (You may need to add a little water if the mixture becomes dry.)
Season, add the parsley and stir. Add the eggs and garnish with cayenne and nutmeg if using. Serve topped with a knob of butter and wedges of lemon.