Mix the white breadcrumbs, suet, parsley, herbs and nutmeg together, season well with salt and pepper, add half the egg and enough milk to moisten thoroughly. Make an incision down the centre of the fish as for filleting, raise the flesh each side as far as possible and fill with forcemeat. Instead of drawing the sides of the fish close together, fill up the gap with forcemeat and flatten the surface to the level of the fish with a knife. Brush over with the remaining egg, coat lightly with pale brown breadcrumbs, put into a fireproof dish and dot a few small pieces of butter on top. Bake for 20–30 min. in a moderate oven (350° F., Gas 4).