Spring roll skins are magical. Made of tapioca starch, rice starch, salt and water they look like thin plastic disks. But give them a brief, 30-second soak in tepid water and they become pliable and translucent. Look for spring roll skins in Asian markets; stored in the kitchen cabinet, they'll keep for months. These can be made up to 4 hours ahead. Once rolled, place on a lightly oiled platter, cover with dampened paper towels and plastic wrap and store at room temperature.