- Combine sugar and water in a small saucepan; bring to a boil. Boil 2 minutes.
- Remove from heat; add 1 cup of mint leaves. Allow to steep for 30 minutes. Strain syrup.
- Place remaining mint leaves and lime juice in a serving pitcher; muddle mint leaves to release oils.
- Pour in mint syrup, rum and club soda; mix well.
- To serve: Pour mixture over ice in a tall glass; garnish with a mint leaf and a slice of lime; serve immediately.