This section is from the book "The American Woman's Cook Book", by Ruth Berolzheimer. Also available from Amazon: The Domestic Arts Edition of the American Woman's Cook Book.
Scale the fish. Split it down the back, clean, wash and wipe dry as usual. Prepare a plank of oak or hickory, about one and one-half inch thick, and put in the oven to heat. If using a gas stove, place it directly under the gas in the broiler, having the side which is to hold the fish nearest the flame.
Rub the fish all over with oil, salt and pepper. Lay it skin side down on the plank, and put the plank on the upper grate of the oven, or under the broiler of a gas stove. Cook about one-half hour, spreading melted fat over the fish while it is in the oven if there is a tendency to dryness. If the fish has roe, the roe may be broiled on the plank beside the fish, or the roe may be boiled, mixed with a little white sauce, well seasoned, and spread over the thinnest part of the fish, five minutes before it is finished, and covered with crumbs.
Have ready freshly mashed potato and form a border of this around the fish by pressing it through a pastry-bag. Set the plank in the oven until the potato has browned, then send to table garnished with lemon and parsley.
The size of the plank will depend on the size of the oven, but it must be at least three inches wider than the fish. White-fish and shad are best for planked fish.