Melt chocolate in small saucepan or in the microwave using 30 second intervals.
Allow the chocolate to cool to about 91 degrees, stirring often. If you don’t have a thermometer, test the temperature of the melted chocolate by putting a drop on your finger. It should feel cool. If it’s hot, let it cool longer.
Pour in corn syrup.
Stir slowly until well mixed. This chocolate mixture will become thick very quickly, so be sure to scrape the bottom of the bowl to incorporate all of the melted chocolate.
Pour mixture out onto a flat surface, using powdered sugar if needed to help shape the dough
Knead until glossy and smooth. If your hands are warm us a plastic dough scraper to knead the modeling chocolate.
Wrap the modeling chocolate in plastic wrap and place in a zip top bag or airtight container.