In a cocktail shaker, add 1 ounce of Bombay Sapphire gin, ¾ ounce of St-Germain, 1 ½ ounces of freshly squeezed grapefruit juice, ½ ounce of Lillet Blanc, and 1 dash of lemon bitters over ice.
Shake until the cocktail shaker is almost too cold to touch (about 15 to 20 seconds).
Strain it into a coupe or a short tumbler, then garnish with a grapefruit peel.
