Elderflower liqueur is sweet, delicate, and floral, like nectar from a spring bouquet.
Microwave sugar and water in a microwave-safe bowl at HIGH 2 minutes. Stir until sugar dissolves. Cool completely (15 minutes). Stir together sugar syrup, elderflower liqueur, lemon juice, and ice cubes. Let stand 20 minutes. Stir in chilled sparkling wine, and serve immediately.