To further improve the classic Amaretto Sour, Portland, Oregon, bartender Jeffrey Morgenthaler uses fresh lemon juice and high-proof bourbon to round out the cocktail, plus egg white for a dash of body and a silky texture. Egg white may seem unusual, but it’s a traditional addition to many sours, including the Whiskey Sour and Pisco Sour.

Morgenthaler’s take is magic. The relatively small amount of high-proof bourbon doesn’t overshadow the amaretto, but instead bolsters the liqueur, allowing it to present strongly alongside tart citrus. Frothy, sweet, sour, nutty and packing a punch, these minor changes create a more balanced cocktail.

Référence : https://www.liquor.com/recipes/amaretto-sour/