In the bottom of the glass, add 1 ounce of simple syrup and a handful of mint leaves. Muddle with a muddler or use the clean bottom of something blunt, like a screwdriver! Add ice to the glass, and pour in the tequila, grand marnier, rum, lime juice and remaining simple syrup. Mix with a long spoon or knife, stirring well to combine. Add another bunch of mint leaves and a lime wedge or two. Top the glass off with club soda (a few ounces until you reach the top!).