Turn the dough out onto a well-floured surface, dust it lightly with flour, and press it down with a rolling pin until it is somewhat rectangular in shape and about ½ inch (1.3 cm) thick. Fold it in thirds like a business letter, and turn it one quarter turn (90 degrees). Lightly flour it and gently press it out again until it is an even rectangle about ½ inch (1.3 cm) thick, fold it in thirds, and turn it another quarter turn. Lightly flour the dough again if necessary to keep it from sticking to the rolling pin, and roll it out to form a very even rectangle measuring 6 x 12 inches (15 x 30cm). Cut it in half, crosswise, then cut an X through each half so that you have eight triangular pieces. Sprinkle the pieces with the remaining 1 tablespoon of sugar. Transfer them to the prepared baking sheet, leaving about ¼ inch (1/2 cm) between them. Bake in the center of the oven until the shortcakes are golden and puffed, about 12 minutes. Slide the parchment paper off the baking sheet and onto a wire rack to cool.