Put it in the oven and when it is done, which can be easily ascertained by lifting a bit of the flesh, you, being American, may garnish the board with mashed and seasoned potatoes, set the board back in the oven till the potatoes are browned and serve. The French, on taking the cooked fish from the oven, merely brush it with a little oil or melted butter, squeeze some lemon juice over, sprinkle a few bits of parsley about, and send the fish thus to the table.
Small fish, such as perch, smelts, etc., are best fried in deep fat or its substitute, first being dipped in egg and rolled in fine cracker or breadcrumbs, then served with a Sauce Mousseline, mashed potatoes or boiled new ones, and a crisp salad.
This Sauce Mousseline is made by beating two eggs in a saucepan, adding a cupful of top milk, butter the size of a walnut and pepper and salt, then stirring over the fire till it begins to thicken. When of the proper consistency, add a tablespoonful of lemon juice and it is ready for the table.
A tart sauce for boiled fish that is much favored in the south of France but which, if it has ever crossed the water, has kept its arrival very quiet, is quite simply made and will be much liked as a decided change. To make it dissolve a tablespoonful of powdered mustard in a half cupful of fish stock and add two tablespoonfuls of white wine vinegar by preference, though other vinegar will do. Let this come to a boil, add two or three slices of lemon and boil a few minutes longer. Take from the fire and add two eggs that have been beaten with a teaspoonful of water. Season with salt and pepper and heat again but do not allow to boil.