For tartar sauce, combine the mayonnaise, sour cream, pickle relish and mustard in a small bowl; mix well. Cover and refrigerate. In a large resealable plastic bag, combine the cornflake crumbs, Parmesan cheese and seasonings. Place the milk in a shallow bowl. Dip fillets in milk, then place in bag and shake to coat. Arrange in a greased 15-in. x 10-in. x 1-in. baking pan. Bake at 450 degrees F for 10-15 minutes or until fish flakes easily with a fork. Serve with tartar sauce and lemon.