Cook syrup over medium heat until reduced by half. Reserve syrup to serve with apples. To make stuffing, combine brown sugar, melted butter, finely chopped walnuts, raisins and ground cinnamon in a small bowl. When apples are cool enough to handle, pack cores with stuffing. Put puff pastry sheets onto a floured board.
Dust tops with additional flour if pastry is moist.
Wrap each stuffed apple with three strips of puff pastry. Begin by repositioning one end of each strip at the bottom of the apple. Wrap the strip all the way around until the other end meets at the bottom. Repeat for each strip. Cut a decorative leaf for each apple from the remaining puff pastry.