Remove heads and fins from the whiting and slit them down the backbones to allow the heat to penetrate easily.
Grease a shallow baking dish and sprinkle in the shallots.
Add the liquid and the butter and bake in a moderate oven, basting frequently with the juice.
By the time the fish is done all the liquid should have evaporated.
Sprinkle with the lemon juice and parsley and serve at once.