Bright, aromatic, and topped with a firm foam cap. Pisco brings the punch, passion fruit juice drives the tropical acidity, and gum syrup rounds it out. Egg white is the key: silky texture and a foam layer that holds the bitters.
Squeeze the key lime and strain it if it has seeds. Measure the pisco, passion fruit juice, and gum syrup before starting; in cocktails, “more or less” charges interest.
Add the pisco, passion fruit juice, key lime juice, and gum syrup to the shaker. Shake gently for 5 seconds just to combine the base and check balance if needed.
Add the egg white, close the shaker, and dry shake for 12 to 15 seconds, without ice. This builds the foam; skipping it asks for a sad, flat sour.
Turn what you find into an experience you can actually bring to your kitchen.
Open, add the ice, and shake hard again for 10 to 12 seconds, until the outside of the shaker is very cold. Hard and short: we want chill, not watery juice with tired foam.
Strain the sour into chilled glasses, letting the foam fall at the end. Serve as soon as it settles, when the surface looks firm and glossy.
Finish each glass with drops of Angostura bitters over the foam. It should be very cold, bright, tropical, and topped with foam that does not collapse in the first minute.
