To make the coffee sugar rim, whisk together the sugar and instant espresso on a shallow dish.
For the chocolate simple syrup, combine cocoa powder, sugar, and water in a small sauce pan. Heat for 5 minutes or until sugar dissolves, stirring frequently. Leftovers can be stored in the fridge for up to a week.
Run a damp clean cloth around the rim of your choice glass. Dip and twist through the coffee sugar until well coated. Spoon in choice amount of chocolate syrup into the bottom of the glass.
In a shaker, combine creme de menthe, whiskey, and coconut rum. Add ice and shake until cold. Strain over ice into the glass and top with mint leaves.