Place the haddock in a roasting pan with healthy knobs of butter and 1 cup of water and cook in a 425°F oven for 10 minutes, then remove from the oven, allow it to cool, and skin it. Save the juice in the pan and roughly flake the fish. Place the rice in a pan, lay your hand flat on the rice, and add enough water to cover your hand. Add a pinch of salt, bring to the boil, and simmer for about 20 minutes, then check the rice and drain off any excess water.
Gently fry the onions in butter in a big frying pan, so that they go soft and sweet rather than brown and burnt. Add the fish and rice and the liquor from the haddock pan, adding more butter if the mixture seems dry or is sticking (this dish is a very good vehicle for butter). When all the ingredients are heated through, squeeze the lemon onto it, season, stir in the egg and parsley, season again, and serve. It is very good by itself, but does go very well with Green Bean Chutney.