Use this for a sugar-based dough to decorate your wedding cake. Knead the dough first before using.
Combine vinegar and 2 tablespoons water in a 1-cup heatproof 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 the bowl of an electric mixer fitted with the paddle attachment, combine the vinegar-gelatin mixture and confectioners' sugar. The pastillage should look like bread dough. (If the pastillage is too dry, add 1 teaspoon of water; if it is too wet, add more confectioners' sugar.) Remove the pastillage, and knead it by hand until the sugar is completely incorporated and the pastillage appears smooth. Wrap well in plastic wrap, and store in an airtight container in the refrigerator overnight.
The pastillage will be rock hard when you remove it from the refrigerator. To soften the pastillage, 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.