Pick apart sufficient cold cooked fish to make a half pint. Rub together the butter and flour, add the milk, stir until boiling, add the salt, soy, red pepper and black pepper. When this is hot add the fish and mushrooms; stand over hot water, without stirring, until the fish is thoroughly heated. While this is heating, trim the crusts from the bread; toast the one side carefully. Have the potatoes ready in your pastry bag with a star tube; press in a rope-like form, or in small rosettes, around the edge of the bread on the untoasted side. Brush the bread with a little melted butter, put them in the oven until the potatoes and bread are a golden brown. Dish these on square paper mats on individual plates, fill the centers with the creamed fish and send at once to the table.
Canned salmon may be used in the place of fresh boiled fish.