Combine liquid ingredients in an ice-filled mixing glass and stir until cold. Strain into a chilled cocktail glass. Cut a thin slice of lemon zest over the surface of the drink and drop it into the glass.
The Improved cocktail is a Jerry Thomas creation, and the Improved Whiskey Cocktail was further popularized (if you can call it that) by David Wondrich, columnist for Esquire and author of Imbibe! (the book, not the magazine).
While a very nice drink, I think it could actually be further improved by either reducing or omitting entirely the simple syrup. While this recipe isnât too sweet exactly, it could stand a little less sweetener.