Shrub cocktails get their tart pucker from vinegar.
Muddle first 2 ingredients in a cocktail shaker to release flavors; add elderflower liqueur and next 3 ingredients. Fill shaker with ice; cover with lid, and shake vigorously until thoroughly chilled (about 30 seconds). Strain into 8 (8-oz.) glasses; top with sparkling wine.
2 restaurants: Pasture and Comfort, Richmond, VA