Which liqueur is the defining ingredient in a classic Grasshopper cocktail?

Crème de menthe is the defining ingredient in a classic Grasshopper cocktail.

The Grasshopper traditionally combines green crème de menthe, white crème de cacao and cream in equal proportions. The mint liqueur supplies both the vivid green color and the drink’s cool mint flavor, while crème de cacao adds chocolate notes and cream softens the mixture.

The drink is strongly associated with Tujague’s restaurant in New Orleans, where it became popular in the early 20th century. A frequent mistake is identifying crème de cacao as the ingredient responsible for the green appearance; crème de cacao is normally clear or brown, depending on the style. The cocktail is generally served shaken and strained, often in a chilled cocktail glass, and is sweeter and richer than spirit-forward classics such as the Martini.