Once the dough had risen knock it back down then break off walnut/golf ball size pieces.
Roll out each piece on a lightly floured surface to around 2-3mm thick, rough circles (as thin as you can basically).
Place each rolled out circle on to the baking sheet, brush with the egg white then generously cover with sugar.
Bake in the oven for 7-10 minutes (depending on the size of your oven and the number of baking sheets you have you will probably need to do this in batches). Keep a close eye on them. You want them to turn a rich brown colour and for some of the sugar on top to have caramelised.
Remove from the sheet as soon as they come out of the oven and leave to cool.