The pisco sour is a sweet-and-tart egg white-based cocktail that highlights the unique flavor of pisco brandy. This unusual Peruvian spirit looks like vodka or other white liquors, but has a crisp, tart, spicy taste. Originally developed in 16th century Chile and Peru, this liquor can be difficult to find at many U.S. retailers. While no other spirit can entirely replace the distinctive flavor of pisco, you do have a few substitution options if you can't acquire this Peruvian liquor.
Grappa
Grappa, also called pomace brandy, is a relatively sharp-tasting beverage made from the grape residue that remains after normal brandy production. Higher quality grappas are smooth-tasting and are similar in strength and complexity to pisco. Unlike pisco, grappa still contains the grape skin, producing a more aggressive tannic bite in the finished drink.
White Tequila
The relatively high alcohol content of pisco means that most ordinary brandies won't produce the same flavor in a pisco sour. Gourmet Sleuth recommends substituting white tequila for pisco when making this beverage. White tequila works best as a direct substitute for non-aromatic piscos made from Quebranta grapes, according to the Latin Kitchen. It may not work as well if your recipe calls for a Mostatel or Italia-based pisco.
Single Malt Scotch
Single malt scotch makes an appropriate substitute for pisco if you already enjoy whiskey sours. The resulting drink should have a similar bite but a smokier taste. The presence of egg white helps distinguish this beverage from a traditional whiskey sour, even with the substitution.
Cachaça
Made from sugar cane juice instead of grapes, this Brazilian liquor has a fruity flavor that works with many of the same ingredients as pisco. Cachaça is slightly sharper than pisco and is a traditional ingredient in the Brazilian cocktail caipirinha.