The Boulevardier is a classic cocktail that was created by Erskine Gwynne, a magazine editor who lived in Paris, France in the 1920s and often drank at famous bartender Harry MacElhone's New York Bar. The recipe is considered a cross between the Negroni and Manhattan because it's made with equal-parts vermouth and Campari with whiskey as the base spirit, and it gained popularity when Harry eventually published the specs in his book Barflies & Cocktails.
Add bourbon, sweet vermouth, and Campari to a mixing glass.
Fill mixing glass with cubed ice.
Using a bar spoon, stir for 30-45 seconds until well-chilled and slightly diluted.
Add a clear ice cube to a lowball glass.
Using a julep strainer, strain into lowball glass.
Garnish with orange peel.