Stir together first 3 ingredients in a medium saucepan over medium-high heat. Bring to a boil, stirring occasionally, and boil 1 minute or until sugar is dissolved. Remove from heat, and let stand 30 minutes. Pour liquid through a wire-mesh strainer into a cruet or airtight container, discarding lemon balm leaves. Cover and chill 4 hours. Garnish, if desired. Syrup may be stored in refrigerator up to 1 month.
*3/4 cup sugar/no-calorie sweetener may be substituted. For testing purposes only, we used Splenda Sugar Blend for Baking.