The Boulevardier is a cousin to the Negroni, made with Campari, sweet vermouth, and bourbon (instead of the Negroni's gin). Normally, it's made with equal parts of each and stirred, but bartender Karl Franz Williams likes to use a touch more bourbon and shake it, for a nice froth on top.
In a cocktail shaker, add Campari, vermouth, and bourbon. For a straight-up boulevardier, fill a coupe glass with ice cubes to chill. Meanwhile, fill the cocktail shaker with ice cubes. Cover and shake briefly, about 5 seconds. Discard the ice cubes from the coupe glass. (If using a rocks glass, fill it with ice cubes.) Uncover the shaker and, using a strainer, pour the cocktail into the glass. Finish by placing a twisted orange peel directly on top of the cocktail. Serve immediately.