Millionaire is a name given to several unrelated cocktails that appeared before and during Prohibition, but the bourbon or rye-based sour became the most popular option that withstood the test of time. The original version used rye, Curaçao, grenadine, and egg white, but modern variations often use Grand Marnier instead of Curaçao and add lemon juice and pastis or absinthe.
To make the cocktail, all the ingredients are poured into a shaker. They are dry shaken (without ice) and then shaken again with ice. Millionaire is mostly served in a coupe glass, and it is typically garnished with a lemon twist. Some recipes use freshly grated nutmeg as a garnish.