Rinse fish thoroughly in cold water; pat dry.
Place fish in a greased 13- x 9- x 2-inch baking dish; add water to cover. Add next 8 ingredients, and dot with 1/4 cup butter.
Cover and bake at 350° for 25 minutes or until fish flakes easily when tested with a fork.
Drain fish and vegetables; reserve pan liquid for Mushroom Cream Sauce. Remove and discard bay leaf.
Prepare Mushroom Cream Sauce, and pour over fish and vegetables in baking dish; broil 4 inches from heating element 5 minutes or until lightly browned on top. Garnish with lemon slices and fresh parsley sprigs. Serve immediately.