A Pisco Sour is a cocktail typical of South American cuisine.The drink's name comes from pisco, which is its base liquor, and the cocktail term sour, in reference to sour citrus juice and sweetener components. The Peruvian Pisco Sour uses Peruvian pisco as the base liquor and adds Key lime (or lemon) juice, syrup, ice, egg white, and Angostura bitters.
There are many ways to make the famous pisco sour, so it's best to know the fundamentals. The basic formula is 3 parts pisco to 1 part simple syrup and 1 part lime juice. With that goes egg white, and a sprinkle of Angostura bitters.
Very tart lime juice is essential. Many recipes call for lemon juice, possibly a translation error from the Spanish word "limon". Limones are actually small South American limes, similar to key limes (also known as"Peruvian lemons").
Shake this cocktail well, so that when you pour it into an old-fashioned glass, you get a nice half inch layer of foam on top.