Melt 2 T butter in a pan, add onion and sauté until transparent; add mushrooms and half the parsley and sauté 8-10 mins, stirring occasionally. Arrange 4 of the fish fillets in the base of a greased ovenproof casserole (11x7-in./28x18-cm works good), spoon over the sautéed mixture and arrange the remaining 4 fillets on top; season with salt and pepper, pour wine over fish and dot with remaining butter. Cover and cook at 350 F for 15 mins; remove dish from oven, strain off liquid and reserve. Blend flour and cream together in a pan, stir in reserved liquid and cook gently, stirring constantly, until thickened and pour over fish. Return dish to the oven and cook a further 10 mins. At serving time, sprinkle with paprika and remaining parsley. Makes 4 servings.