Here is a drink I call 'Royal Cup' - they are fantastic. You can serve them in martini glasses or champagne flutes. It is easy to make a pitcher of them for small gatherings or serve them up one at at time.
1 ounce Grand Marnier
3 drop bitters
4 ounces Astoria Lounge Prosecco
Relax and be Royal! 'Look Charles, it thinks I'm fancy...'