Combine the Parmesan, flour, and a pinch of salt in the dough mixer. Add the butter parcels gradually.
Making the dough by hand is easy when only a small amount.
Mix the egg yolk with the water and lime juice and pour into the mixing bowl. Continue mixing until all is well combined.
Refrigerate the dough for an hour wrapped in cling film.
Roll out the Parmesan dough to about 5 mm.
Cut round or square shaped crackers and arrange them on a baking tray. Sprinkle some Piment d’Espelette and Fleur de sel over the unbaked shortbread.If you have time, refrigerate the unbaked shortbread for another 20 minutes before baking.
Preheat the oven to 175°C and bake the cookies for 10-12 minutes until they get a light-pale colour around the edge.Allow to cool down on a wire rack.
Notes
Parmesan can be salty depending on the age of the cheese, taste first and decide then to add extra salt to the dough or not.
Baking time depends on the thickness of the crackers.
The lime juice is optional but the idea is to bring a little zing to the taste and to reduce the butter flavour.