1. Cut 2 large limes into wedges. In a blender combine the lime wedges (reserve 1 wedge), 2 cups of water, and 2/3 cup sugar. Cover and blend about 30 seconds or until limes are unevenly chopped. (Don't make a uniform puree.)
2. Strain lime mixture through a fine-mesh sieve into a large serving pitcher to remove the lime chunks. Stir in 2 additional cups of water. Cover and chill for 1 to 12 hours.
3. To serve, stir 1/4 to 1/2 cup light rum into the chilled lime mixture. Run the cut side of a lime wedge around the rims of 8 serving glasses and dip rims in superfine sugar.
4. Use a mortar and pestle to bruise 1/2 cup fresh mint leaves just enough so they release their flavor. (Don't make a paste.) If you don't have a mortar and pestle, place mint leaves in a small bowl and crush with the back of a spoon. Place some of the bruised leaves in each glass. Fill glasses with ice cubes. Pour chilled lime mixture into glasses. If desired, garnish with quartered limes. Makes 8 servings.
Superfine sugar, also called baker's sugar, is perfect for making cold drinks because the extremely fine grains dissolve easily into cold liquids. It's also great in iced coffee and tea and homemade lemonade. You can find superfine sugar in the baking aisle of your local supermarket.
In just 10 minutes you can whip up a raspberry variation of this classic drink.
Thaw 1 cup fresh or frozen raspberries. (If frozen; do not drain.) Place sugar in a shallow bowl. Rub 1 lime wedge around the rims of two 6- to 8-ounce cocktail glasses. Dip rims into sugar to coat; set aside. If desired, set aside several raspberries for garnish. Place the remaining raspberries in a food process or blender. Cover and process or blend until smooth. Strain berries through a fine-mesh sieve; discard seeds. Set aside. Divide 1/3 cup lightly packed fresh mint leaves, coarsely snipped, between the prepared cocktail glasses. Fill glasses three-fourths full with ice cubes. In a cocktail shaker combine 1/4 cup (2 ounces) light rum and the strained raspberries. Add ice cubes to fill shaker almost full; shake until very cold. Strain into the ice-filled glasses. Slowly pour 2/3 cup chilled carbonated water into glasses. If desired, garnish with the reserved raspberries and fresh mint sprigs.