Table the gianduja until it is firm enough to hold its shape when piped.
Fill a pastry bag fitted with a #5 or #6 straight tip with the gianduja and pipe cylinders 16 in/41 cm long onto a parchment-lined sheet pan. Allow to set until firm, 10 to 15 minutes.
Roll out the marzipan on a clean marble surface into a rectangle 16 in/41 cm long and ¼ in/0.6