Fill a cocktail shaker with ice cubes to chill it.

Add St-Germain, lavender syrup, and soda water to the shaker.

Shake the mixture vigorously to ensure thorough blending of the ingredients.

Strain the mixture into a chilled cocktail glass.

Top it off with prosecco, allowing the effervescence to mingle with the flavors below.

Give the cocktail a gentle stir to marry the ingredients harmoniously.

Garnish with a sprig of fresh lavender to add a touch of visual appeal and aromatic sophistication.