Clean the fish, cutting off the fins. Make the letter “S” on the sides with a sharp knife. Rub well inside and out with pepper and salt. Butter a stewpan and put in one large chopped onion and a wineglassful of White Wine. Place the Fish in the pan, put in the oven and let it bake about twenty minutes, having been careful to place lumps of butter over it and basting frequently. When done, carefully lift the Fish out of the pan and put it into the dish in which it is to be served. Take the gravy in which the Fish has been cooked and add about a cup of oyster liquor, the juice of one lemon, two tablespoonfuls of chopped mushrooms, one tablespoonful of minced parsley, thyme and sweet marjoram, ten allspice, one clove of garlic, a little Cayenne, and salt and pepper to taste. Mix all thoroughly over the stove, adding a little butter if the gravy adheres too much to the pan. Pour over the Fish, and garnish with whole mushrooms and slices of lemon laid alternately upon Croutons or dried toast cut in diamond shapes.