Thinly sliced citrus fruits, lightly candied in sugar syrup, make an elegant topping for tarts and tartlets. They provide a concentrated flavor with a delightful hint of bitterness.
Combine the sugar, corn syrup, and water in a heavy-bottomed saucepan and bring to a gentle simmer. Continue simmering, stirring constantly, until all the sugar dissolves.
Cut the ends off the orange, set the orange on end, and cut it in half vertically. Lay the orange halves their cut sides and slice both halves crosswise into ⅛-inch-thick slices. You should end up with about