To freeze piadina: Cool the piadine on a rack. Lay in single layers on a tray separated by waxed or parchment paper. Freeze for several hours. For longer freezing, pack the rounds, separated by small sheet of waxed or parchment paper, into a resealable plastic freezer bag. To reheat: A single piadina is easily reheated in a hot cast iron skillet on a griddle for 1 to 2 minutes per side. (No need to thaw beforehand). Or, place in a toaster oven for about 2 minutes until heated. To reheat the entire batch, remove the paper between the rounds and sprinkle each round lightly with water. Stack the rounds in a large piece of aluminum foil. Bake in a preheated 325??F oven for 40 minutes, or until heated through.