Sauce a la Normande

Cut three pounds of bony fish into pieces, such as sheepshead, bass, blackfish, redsnapper, etc., let the pieces be of a quarter of a pound each; put them into a saucepan with two minced onions, two ounces of mushroom parings, some parsley, a bay leaf, the same quantity of thyme and two cloves of garlic, moisten with a quarter of a bottle of white wine, three pints of water, two gills of oyster liquor and let the whole cook slowly for thirty minutes, then strain the sauce through a fine sieve, and add to it one quart of veloute (No. 415), another quarter of a bottle of white wine, and reduce it all; just when ready to serve, thicken the sauce with four egg-yolks and incorporate into it two ounces of butter and the juice of a lemon; season well and finish by straining once more through a tammy (No. 159).