Perch, Normandy Style

Scale and clean the perch, put some chopped onions at the bottom of a flat stewpan
and put in the perch, with a bunch of parsley, some trimmings of fresh mushrooms,
a little salt and white wine to cover. When the liquid is boiling move the
stewpan to the side of the fire and keep the contents simmering for fifteen minutes.
Prepare a garnish with some quenelles, mushrooms, oysters, and mussels, reserving
the liquor of the oysters and mushrooms. Drain the liquor off the fish through a fine
hair sieve into a sautepan and boil it till reduced to half; then take the pan off the
fire, thicken the sauce with kneaded butter, divided into small pieces, stirring all the
time, then add a liaison of the yolks of three eggs. Put the perch on a hot dish, pour
the sauce over it, put the prepared garnish round, glaze it under a salamander and
serve.