1  dressed whitefish, bass, or lake trout (2 to 3 pounds) Salt 1  cup chopped cooked shrimp 1  cup chopped fresh mushrooms 1  cup soft enriched bread crumbs 1/2 cup chopped celery 1/4 cup chopped onion 2  tablespoons chopped parsley 3/4 teaspoon salt Few grains black pepper 1/2 teaspoon thyme 1/4 cup butter or margarine, [...]