Preparation / Directions:
Place fillets on a greased rack and steam over salted water until fish is cooked, about 10 minutes or less. Remove from the heat and keep warm. Discard the liquid.
In a saucepan combine melted butter, flour, mustard, 1/4 teaspoon salt and the pepper. Stir in 1 cup hot milk. Cook and stir over moderate heat until smoothly thickened. Add egg and parsley; mix well.
Pour sauce over fish and reheat for several minutes.
Adapted from a recipe in "Froze Fillets", Department of Fisheries and Oceans Canada