Plus: Ultimate Cocktail Guide
In a bowl, using a wooden spoon, crush the mint with the sugar until the mint is coarsely chopped and the sugar is pale green. Add the lime juice, rum and bitters and stir to dissolve the sugar.
Strain the mixture through a coarse strainer into a small pitcher. Pour into tall glasses over ice and top each drink with 1/2 cup of the club soda. Garnish with mint sprigs and serve.