Preparation Place enough sugar on small plate to reach depth of 1/4 inch. Run lime wedge around rim of 4 Martini glasses to moisten. Dip rims into sugar on plate. Blend rum, lime juice, and 1/3 cup sugar in blender until sugar dissolves. Add 4 cups ice; blend until slushy and almost smooth, adding up to 1 cup more ice, if desired. Add 12 mint leaves and blend until small green flecks appear. Pour into prepared glasses. Garnish with mint sprigs.
Preparation Place enough sugar on small plate to reach depth of 1/4 inch. Run lime wedge around rim of 4 Martini glasses to moisten. Dip rims into sugar on plate. Blend rum, lime juice, and 1/3 cup sugar in blender until sugar dissolves. Add 4 cups ice; blend until slushy and almost smooth, adding up to 1 cup more ice, if desired. Add 12 mint leaves and blend until small green flecks appear. Pour into prepared glasses. Garnish with mint sprigs.