Stir, strain, straight up, cocktail glass, garnish.
Original 2005 recipe through ~early 2008 was bourbon, Averna, and homemade cherry-coffee bitters. Later in 2008 the drink changed to its present form.
Todd Smith originally created this cocktail at the Cortez restaurant's bar in San Francisco in 2005 using bourbon rather than rye. He brought the drink with him as bar director of Bourbon & Branch which opened in 2006. https://www.sfgate.com/wine/article/The-cosmo-free-zone-Bartending-puri… In 2007 Gaz Regan stated that the Bourbon & Branch version used bourbon, Averna, and "a couple of dashes of Todd Smith's homemade cherry-coffee bitters." https://www.sfgate.com/wine/article/the-manhattan-project-a-bartender-s…
Smith left Bourbon & Branch in early 2008, and they eventually ran out of his bitters. https://sf.eater.com/2008/3/6/6802155/eaterwire-changes-at-bourbon-bran…
Based on the 2008 Washington Post article recipe, the drink had evolved to its present widely known form a few months later: rye, Averna, a dash of Angostura Aromatic bitters, plus a dash of orange bitters.