Cook this on top of your range in a utensil attractive enough to come to the table, or use an electric frying pan.
Melt 2 tablespoons of the butter in the bottom of the cooking utensil; remove from heat.
Arrange half the potatoes in the bottom of the pan.
Cover with half the onions.
Combine the salt, pepper, bay, and allspice; sprinkle about 1/3 of the mixture over onions.
Make a layer of the fish fillets; sprinkle with 1/3 of the spice.
Make a layer of remaining potatoes, then a top layer of onions.
Sprinkle with the remaining spice.
Dot the top with the rest of the butter.
Cover the pan and place over lowest heat for about 2 hours, or until the potatoes are tender (or cook it in an electric pan set at 175°).