Pastillage is a sugar paste that is shaped into sculptural designs and then dried. Dried pastillage breaks easily; make four arches so you have plenty of spares. Use this recipe when making our Rose-Garland Wedding Cake.
Combine vinegar and 2 tablespoons water in a 1-cup heat-proof measuring cup. In a microwave, heat on high until hot to the touch.
Gently sprinkle the gelatin over the vinegar mixture, and let dissolve, approximately 5 minutes. There should be no grains of gelatin left. If necessary, reheat the mixture in a microwave a few seconds, and continue stirring until all grains of gelatin are completely dissolved in the vinegar mixture.
In bowl of an electric mixer fitted with paddle attachment, combine vinegar-gelatin mixture and the confectioners' sugar on low speed, about 1 minute or until mixed. The pastillage should look like bread dough. (If pastillage is too dry, add 1 teaspoon of water; if it is too wet, add more confectioners' sugar.) Transfer pastillage to work surface dusted with cornstarch; knead it by hand until sugar is completely incorporated and pastillage appears smooth. Wrap well in plastic wrap, and place in an airtight container; transfer to refrigerator to chill overnight.
The pastillage will be rock hard when you remove it from the refrigerator. To soften it, place it in a microwave for approximately 20 seconds. Check the consistency of the pastillage to see whether it has softened; if not, microwave it another 10 to 20 seconds. Knead the pastillage to a smooth consistency; you may need to sprinkle a little cornstarch on your hands and the work surface to keep the warm parts of the pastillage from sticking to the work surface. Wrap well in plastic until ready to use.
Make the plaque: On a smooth work surface dusted with cornstarch, roll out a 3-inch-diameter ball of pastillage to 3/8 inch thick. Cut out 2 ovals 3 1/2 inches long by 2 3/4 inches wide, or the size of the largest cutter of the Ateco oval cutter set; set these plaques aside to dry overnight on a cornstarch-dusted flat surface such as a sheet pan. (The second plaque is a spare.)
Make the arbor: Roll out one-fourth of the remaining pastillage to make a strip 1/8 inch thick and at least 20 inches long. Working quickly, because pastillage dries very rapidly, cut decorative border on each long edge with a straightfrill border cutter to make 1-inch-wide strip; cut to 20 inches long. On a cornstarch-dusted sheet pan, bend strip into an arch that will reach over the cake topper, its ends abutting ends of oval plaque. Place arch on its side on pan; let dry overnight. Repeat with remaining pastillage to make four arches.