The Black Manhattan was created in 2005 at San Francisco bar Bourbon & Branch by bartender Todd Smith. It’s a simple variation on the classic Manhattan, with bittersweet Averna amaro replacing the sweet vermouth and with a second type of bitters added. These adjustments result in a heavier and slightly more bitter rendition of its forebear, with additional depth of flavor from the amaro’s herbal and caramel notes.

Référence:
https://www.liquor.com/black-manhattan-cocktail-recipe-5184291