1 oz aged rum (3 years old at least, preferably 5+)
1 oz aged tequila (either a resposado or a young-ish anejo seem to work)
1 oz sweet vermouth (preferably Italian)
2 dashes aromatic bitters (we'll be using a fantastic ras-el-hanout bitters at the restaurant)
2 dashes orange bitters
2 dashes celery bitters
2 drops liquid smoke (yes, drops)
Stir and strain into a cocktail glass. Garnish with a lime wheel.
The recipe for this version is a little more complex, but if making a bunch of them you can premix the last five ingredients. Better yet, use a good embittered vermouth like Carpano Antica or Cocchi Torino, adding only celery bitters and liquid smoke.