Mix 3 tbsp red wine with the cornflour until smooth, then mix in all the wine. Heat stock in a pan, then pour in the red wine mixture and redcurrant jelly, stirring until thickened. Cover the surface with cling film to stop a skin forming. Chill for up to 2 days. To serve, reheat in a pan until bubbling, then stir in the turkey juices and transfer to a warm gravy boat.