Dry shake all ingredients (no ice) for 10 seconds to emulsify. Add ice and shake hard for 12 seconds. Double-strain into a coupe. Drop 3 dots of Angostura on the foam and run a pick through to create the swirl pattern.
1860s, originally called a 'Stone Sour' or 'Boston Sour' when egg white was added. The benchmark cocktail for proving a bartender can shake.
Coupe, no ice, foam intact. If guest declines egg white, use FiFo or omit; do not substitute simple syrup.
Bright acid, lush texture, restrained sweetness. The foam should be pillowy, not flat.
Costing is directional. Confirm against current beverage grid when invoices update.