Melt chocolate in a double boiler. Remove from heat and stir in syrup. Mix until chocolate starts to pull together to form a dough. Wrap dough in plastic wrap and chill for at least 8 hours in the refrigerator. After the dough has chilled, dust work surface with sugar. Begin to knead and shape the dough. Dough will keep at least 2 weeks (in plastic wrap) in the refrigerator.