Line a baking tray with parchment paper and set aside. Place a piece of parchment paper about 10x10-inches on a work surface.
Use a pastry brush to lightly rush the water over the surface of the pastry.
Sprinkle half of the sugar evenly over the surface of the pastry. Use a rolling pin to lightly press the sugar into the dough.
Fold the left and right sides of the pastry inwards so they meet in the center. Sprinkle the remainder of the sugar over the pastry and use the rolling pin to lightly press this sugar into the dough.
Fold the left and right side of the pastry inwards again, so they meet in the center again, and then fold the pastry in half lengthwise.
Wrap this pastry log tightly in plastic wrap and refrigerate for 30 minutes.
Preheat the oven to 400℉.
Remove the pastry log from the fridge and place it on a cutting board. Using a very sharp knife, cut the log into about 20 slices, each one ½-inch wide. Lay the slices flat on the baking tray about 2 inches apart. Sprinkle a pinch of sugar on each cookie.
Bake the cookies for 10 minutes, then flip them over and bake for an additional 5 to 7 minutes, until they are golden and crispy. Keep an eye on them in the final minutes of baking as they can go from perfect to scorched in a matter of seconds!