Mix a double batch of the sugar mold recipe. Dust half ball pan with cornstarch to prevent sticking. Pack sugar mixture into pan, pressing firmly with heel of hand. Scrape a metal spatula at a 45° angle over pan to remove excess sugar. Unmold at once by placing cardboard circle over pan and turning upside down. To loosen, tap top of pan with spatula and carefully lift pan off. Allow to dry 3 to 4 hours.