For each cocktail, you'll need:
- 2 oz fresh grapefruit juice
- 1 oz rosemary simple syrup
- 3 oz chilled champagne or sparkling wine
- 1 small sprig of fresh rosemary
- Ice cubes
The rosemary simple syrup can be made by heating equal parts sugar and water with fresh rosemary sprigs. Let it cool and strain before using.