The classic sour format, dating back to the mid-19th century, calls for a spirit, lemon or lime juice, and a sweetener. A frothing element such as egg white or aquafaba (the liquid you’d usually drain from a can of chickpeas) is optional and adds a lovely layer of foamy texture atop the drink, which you can then decorate with bitters. If this format sounds familiar, it’s because many drinks follow it, such as the Gimlet—essentially a Gin Sour that calls for lime juice rather than lemon—and the Daiquiri and Tommy’s Margarita. (You’ll want to omit the egg white in all three of these drinks, though.)

This recipe calls for a London dry gin, but feel free to switch it up with different types if you like; an Old Tom gin or even genever, gin’s Dutch predecessor, both work well. And feel free to dial back the lemon juice and crank up the simple syrup by a quarter of an ounce if you prefer a sweeter version of the drink. There’s really no wrong way to make a Gin Sour.

Référence :
https://www.liquor.com/gin-sour-cocktail-recipe-5101079