Preheat oven to 425. Spray w 13x9x2 inches baking dishes.
In a shallow bowl, combine sour cream and soup mix. Place bread crumbs in another shallow bowl (I use a pie pan). Cut fish into serving size pieces; coat with the sour cream mixture, then roll in the crumbs.
Place in two greased 13x9x2 inch baking dishes. Drizzle with the butter. Bake, uncovered, at 425 for 12 minutes. Sprinkle with the parmesan cheese; bake 2-6 minutes longer or until fish flakes easily with a fork.