egg sauce
1/4 teaspoon dry mustard
1/4 teaspoon salt
2 cups milk
1 hard-cooked egg, chopped
2 tablespoons butter
2 tablespoons flour
1 tablespoon chopped
few grains pepper
parsley

Place filets 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.