Add the spiced rum, lime juice and demerara syrup into a shaker with ice and shake until well-chilled.
Double-strain the drink into a Collins glass with fresh ice and a mint sprig.
Top with club soda.
Garnish with a mint sprig, and slowly pour the liqueur over the leaves and the top of the drink.

*Homemade spiced rum: Add 1 stick of cinnamon, 5 crushed cloves and 3 crushed star anise pods to one 750 mL bottle of aged rum. Let steep for at least 12 hours or until desired flavor is achieved, then strain out solids. Add the rum back into the bottle or another sealed container.

Recipe and image from liquor.com