Lillet is a noted French wine-based aperitif, which comes in three different flavors: blanc, rosé and rouge. While it can be served alone and chilled as a dinner wine, I love adding it to cocktails.
In a small saucepan over medium heat, whisk together sugar with 1 cup of water until the sugar has dissolved. Stir in the lavender then bring the mixture to a boil then lower heat to medium-low and simmer until thick and syrupy, about 15 minutes.
Remove from heat and use a fine mesh strainer to strain the lavender flowers from the simple syrup. Let cool completely.
The simple syrup can be made ahead of time and stored, refrigerated, in an airtight container for up to a week.
For the sparkling lavender cocktail:
Fill a cocktail shaker with ice. Add the Lillet blanc, lemon juice and ½ ounce of the lavender simple syrup and shake vigorously.
Strain the cocktail with a cocktail shaker into a chilled 5-ounce coupe glass.
Top off with champagne. Garnish with sprigs of lavender and serve immediately.