This cocktail leans into the traditional sour format by including egg white for a luxuriously smooth texture and frothy top.
Add the melon liqueur, pisco, lemon juice, yuzu juice, simple syrup to a cocktail shaker filled with ice, and and shake 10–15 seconds until well-chilled.
Remove the ice from shaker and add the egg white. Shake vigorously for an additional 10 seconds.
Double-strain through a fine-mesh sieve into a chilled coupe glass.
Garnish with an edible flower (optional).