Unroll a 320g sheet ready-rolled puff pastry. Sprinkle over 100g grated parmesan, then lightly roll the cheese into the pastry using the rolling pin.
Fold the short ends of the pastry a quarter of the way in.
Repeat so the pastry folds up and meets in the middle. It should look like an open book.
Fold the pastry over again so it looks like a log. Cut it into 1-2cm wide slices, then reshape them so they’re nicely rounded. Lay on a baking sheet, lightly brush with 1 beaten free-range egg, then bake at 200°C/180ºF/gas 6 for 10-12 minutes until crisp and golden.