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.

When dry, turn sugar mold over and carefully hold in palm of hand. Do not squeeze or move molded sugar while holding or it will crack. Use a spoon to mark 1/4 in. thick shell on the inside rim. Gently scoop out remaining soft sugar. Smooth inside and edge with your fingers.

Place molded sugar, round side down, on cardboard circle to finish drying about 24 hours, or place on cookie sheet in 200°F oven for 20 minutes. Allow to cool to room temperature before touching.