Pisco Sour
Pisco Sour: Pisco, Lemon juice, Sugar, Ice and Egg White. Served in a cocktail glass. Garnish: bitters.

The Spec
Method
Vigorously shake and strain contents in a cocktail shaker with ice cubes, then pour into glass and garnish with bitters.
Served in a cocktail glass. Garnish: bitters.
Spec held as sourced — TheCocktailDB. The house never guesses a drink.
What to pour
Bottles in the cellar for each line of the Pisco Sour spec:
Drinks that share this spec
Shares Egg White and Sugar with Acapulco. If your shelf makes Pisco Sour, it is already most of the way to these:
Acapulco · Boxcar · Brandy sour · Caipirissima · Egg Nog #4 · French 75 · Frosé · Frozen Daiquiri