Chill the champagne flute or coupe glass with ice while preparing the drink. Remove ice before mixing.
Squeeze fresh grapefruit juice and strain through a fine mesh strainer to remove pulp.
Pour elderflower liqueur and grapefruit juice into the chilled glass.
Gently stir with a bar spoon to combine.
Slowly top with chilled prosecco or champagne.
Garnish with a grapefruit twist or edible flower
Notes
The drink works best with fresh-squeezed pink grapefruit juice rather than store-bought.For a non-alcoholic version, replace the prosecco with sparkling water and use elderflower syrup instead of St. Germain.Store leftover fresh grapefruit juice in an airtight container in the fridge for up to 3 days.Pre-chill all ingredients for the best results and most bubbles in the final drink.