Loosely translated, a boulevardier is a man-about-town. The cocktail by the same name was created by Erskine Gwynne, the publisher of “Boulevardier,” a magazine for expats living in Paris in the 1920s. It’s a tidy story, just like the drink it inspired. Equal parts whiskey, vermouth and Campari, the Boulevardier is both adaptable and adored for its balance of bitter, boozy and sweet. Choose your ingredients wisely. The best Boulevardier, like the best Negroni, hinges on a happy marriage between base spirit and vermouth.