Vermouth is a fortified and aromatized wine that plays a starring role in many classic cocktails and is also enjoyed on its own. It comes in two primary styles: dry and sweet. While they share the same foundational ingredients—wine, botanicals, and a fortifying spirit—their flavor profiles, uses, and even histories diverge in interesting ways.

Invented in the 1920s by Erskine Gwynne, an American-born socialite, the Boulevardier is a deliciously smooth and rich cocktail.