Cut crescent shapes out of grapefruit peel with a small cookie cutter or aspic cutter. Slide shapes onto cocktail picks; set aside.Advertisement
Add freshly squeezed grapefruit juice and club soda to the bottom of a rocks glass.
Add lemon juice, gin, and egg white to cocktail shaker and shake 30 seconds to combine. Add 3-4 ice cubes and shake until very frothy, about 45 seconds more. Strain through fine mesh sieve into glass and allow foam to rise to top. Gently pour grapefruit syrup down the side of the glass, letting the syrup settle at the bottom of the glass. Garnish with grapefruit peel cocktail picks.