 The pisco sour 's initial recipe was that of a simple cocktail . According to Peruvian researcher Guillermo Toro @-@ Lira , " it is assumed that it was a crude mix of pisco with lime juice and sugar , as was the whiskey sour of those days . " As the cocktail 's recipe continued to evolve , the bar 's registry shows that customers commented on the continuously improving taste of the drink . The modern Peruvian version of the recipe was developed by Mario Bruiget , a Peruvian from Chincha Alta who worked under the apprenticeship of Morris starting on July 16 , 1924 . Bruiget 's recipe added the Angostura bitters and egg whites to the mix . Journalist Erica Duecy writes that Bruiget 's innovation added " a silky texture and frothy head " to the cocktail . 
