Poach fish in lightly salted water. Flake and set aside.
In a medium saucepan, melt butter. Add onion and celery and sauté lightly. Blend in flour, salt, pepper and tomato paste and cook for 2 minutes.
Gradually whisk in milk and cook, stirring constantly, until it thickens.
Add heavy cream, sherry wine and flaked fish and heat thoroughly. Do not boil and do not overcook fish. Garnish with fresh parsley.
Contributed by Joyce Taylor