With cake week under their belts, the 11 remaining bakers must now prove themselves with biscuits. The signature challenge is to create 24 biscotti. Twice baked, these Italian specialities have to be crammed with flavour with a crisp crunch. It's a delicate balance between under-baked and bendy or over-baked and rock hard. Paul chooses the technical challenge, arlettes, a labour-intensive reverse puff pastry biscuit from south-west France. Wafer thin, flaky and swirled with cinnamon, delicious to eat but devilishly difficult to make. And finally, the showstopper is to create and build an edible biscuit box filled with 36 biscuits of a different flavour. Judges Mary and Paul want to see the bakers exercise their creative muscles with clever construction and beautiful decoration, while not forgetting that flavour is king. The pressure is on, and the clock is ticking. Who will claim Star Baker, and who will be leaving the Bake Off tent?