Roll puff pastry into a 2-mm thick sheet, at least 17 cm wide by 22 cm long. Brush off any loose flour. Dust the pastry with granulated sugar on one side. Bush off the excess. Prick the pastry with a fork.
Place a piece of parchment paper on a baking sheet. Place the pastry, sugared side down in the center of the paper. Cover the pastry with another piece of parchment paper. Place the pastry in a refrigerator to rest for 30 minutes.
Preheat oven to 191°C. Place two additional baking sheets on top of the pastry-parchment stack to prevent the pastry from rising to high. Bake 25 to 30 minutes, until the bottom of the pastry starts to brown.
Remove the pastry from the oven and preheat broiler. Remove the top baking sheet and parchment paper. Liberally sprinkle powdered sugar over the hot pastry. Transfer pastry to a plain baking sheet without the parchment paper. Brown under the broiler for a short time until the sugar melts and begins to caramelize.
When cool, using a serrated knife, trim the edges of the pastry to produce a single 16 by 21-cm piece. Cut the pastry lengthwise into two 8 by 21cm pieces. Cut each of these pieces into three 7 by 8-cm pieces.