2 pieces curled lemon rind or lemon wheels (for garnish)
1. Peel off 2 pieces of lemon rind with a peeler or knife, doing your best to get as little pith on the rind as possible, and twist them over your glass to get some of the oils and essence from the lemon, then wipe the rind around the inside of the glass. You can use these as twists if they are still in tact, or twist new pieces of rind around your finger to make them curl for the garnish. Alternatively, you can use sliced lemon wheels.
2. In a shaker, combine your gin, St. Germain, and lemon juice. Fill with ice and shake vigorously for 15-20 seconds. Strain into your glasses and top off with Prosecco or Champagne. Garnish with a lemon twist or wheel and serve.