We used a meat mallet to crush some of the candy for the top of the cake. To save time, crush your own favorite holiday candy.
Generously oil the bottom and sides of a 15- x 10-inch jelly-roll pan. Stir together granulated sugar, 1/2 cup corn syrup, and 1/2 cup water in an oiled 3 1/2-qt. heavy saucepan over medium heat until a candy thermometer registers 300° to 310° (hard-crack stage, about 15 to 20 minutes).
Remove from heat, and carefully stir in peppermint flavoring until well blended; quickly pour mixture onto prepared jelly-roll pan. Cool 45 minutes or until completely cool. Carefully break into pieces.
Carefully brush or dip edges (some edges will be jagged and sharp) of candy pieces with remaining 1/4 cup corn syrup, allowing excess syrup to drip off. Sprinkle with clear sparkling sugar.