To Brûlée the Orange Slices
Slice the orange into approximately 1/8″ slices. In a medium skillet, combine the water and sugar and bring to a boil. Add the orange slices and cook over moderate heat, turning them occasionally, until the liquid is reduced to a thin syrup and the orange slices are translucent, about 20 minutes.
Reduce the heat to moderately low and simmer until the syrup is thick and the slices are tender but still intact, turning occasionally, about 10 minutes. Transfer the orange slices to a rack to cool. Reserve the syrup for another use.
To Make the CocktailCombine bourbon, orange juice, sherry, and ginger liqueur in a cocktail shaker with a handful of ice cubes. Shake vigorously until shaker is ice cold and then strain the cocktail over ice into two rocks glasses. Garnish each drink with an orange slice.