1. In a large pitcher, combine lemon juice and lime juice; add mint leaves and Simple Syrup. Using a muddler or the back of a wooden spoon, crush leaves and stir together well. Add cucumber and ice. Pour lemonade and club soda into pitcher. Serve immediately.

Simple Syrup

1. In a small saucepan, combine sugar and water. Cook over medium-high heat, stirring, until sugar dissolves and mixture comes to a boil. Transfer to a heat-proof pitcher and refrigerate until well chilled, about 30 minutes. (Can be made ahead. Store in an airtight container in the refrigerator up to 2 months.) Makes 2 cups.