2⁄3 cup white rum
1/2 c mint sprigs, plus more for garnish
1⁄4 cup sugar
2 tablespoons fresh ginger, minced
2 cups club soda
Juice the limes. You should wind up with about 1/4 cup of juice. Reserve the juiced halves. In a bowl, mash the lime halves, juice, rum, mint, sugar, and ginger with a spoon or masher. Allow it to sit for about 20 minutes, and then strain into a bowl. Discard the solids. Fill 4 glasses with ice, 1/2 cup rum mixture and 1/2 cup club soda. Garnish with mint sprigs.