Juice the lemon.
Fill a chilled cocktail shaker with ice. Add 1 ounce gin and 1/2 ounce of the lemon simple syrup.
Shake well and strain into your cocktail glass of choice. I would go with a champagne coupe or flute. Given I was styling a Valentine's shoot, I used Sugar & Cloth's blush pink coupe glasses.
Top with the prosecco.