Place a cocktail mug in a refrigerator until chill completely.
Take a cocktail glass and place 1 ounce of Bourbon, 1 ounce of dark rum and ½ ounce Grand Mariner in it. Now, stir all this ingredients for few seconds until mix well. Set it aside for some time.
Meanwhile, take a cup and pour 3 to 4 ounces of boiling water in it. Add ½ tablespoon of superfine sugar to the boiling water. Stir it until the sugar dissolves completely.
Now pour this sugar mixture into the liquor mixture and stir again until both of the mixtures combine properly. Strain it into the pre-cooled cocktail mug.
Toss in a thin wheel of lemon and enjoy.