Add gin, pink grapefruit juice, red bitter liqueur, and elderflower liqueur to a cocktail shaker.
Fill with ice and shake hard for 10–12 seconds.
Fine strain into a chilled coupe glass.
Express a grapefruit zest twist over the surface of the drink to release the oils, then place on the rim as garnish.
The Old Friend originated in Aspen, Colorado, and is considered a modern classic in the aperitivo genre - the combination of elderflower and Campari-style bitter with grapefruit is deceptively simple but exceptionally well-balanced.
My Bar Shelf reads your shelf and shows you every cocktail you can make from what you already own, including Old Friend.