Adapted from Food & Wine
1 ounce London dry gin
1/2 ounce St-Germain elderflower liqueur
1 ounce fresh grapefruit juice
1/2 ounce fresh lemon juice
1 large basil leaf, for garnish
In a cocktail shaker, combine the gin, elderflower liqueur, grapefruit juice and lemon juice. Add the ice and shake well. Pour through a fine strainer into a chilled coupe and garnish with the basil leaf.