1/2 cup loosely packed mint leaves
1 tablespoon instant-dissolving sugar
2 ounces Bacardi Limón rum
1/2 ounce fresh lime juice
1/2 ounce Gosling's Black Seal rum
Garnish: lime wedge and mint sprig
Place 1/2 cup mint in a highball glass with sugar and muddle quickly together, taking care not to smash the leaves. Fill glass with ice cubes, add the Limón rum, fill glass two thirds full with club soda, and add lime juice and black rum. Stir quickly and garnish with a lime wedge and a mint sprig.