To skin hazelnuts, rub the still-warm toasted nuts in a tea towel, to get off as much of the skins as possible. The nuts can be toasted in a 350ºF/180ºC oven for about 10 minutes first. If you want to make your own candied citron, you can find my recipe at that link. You'll often see Panforte baked on rice paper (or made of another edible starch), which is harder to get than parchment paper. You can buy sheets of wafer paper online, and cut them to size.