The Chandelier Bar at Las Vegas's Cosmopolitan Hotel (winner for Best Hotel Bar in the 2014 Saveur Culinary Travel Awards) serves this alluring concoction, the "Planet of the Grapes," which blends Pavan, an orange blossom–infused liqueur, with vodka, chamomile syrup, and sparkling wine.
In a medium pot over medium heat, stir together the sugar and 1 cup water, then bring to a boil and cook, stirring occasionally, until the sugar dissolves, 1–2 minutes. Remove from the heat, stir in the chamomile flowers and lemon zest, and set aside to cool to room temperature.
Strain the syrup, discarding any solids. Fill a cocktail shaker with ice, then add ½ ounce of the chamomile syrup, the lemon juice, Pavan, and vodka. Shake well, then strain into a chilled flute. Top with prosecco and garnish with edible flowers, if you like. (Use the remaining syrup for more cocktails.)