How to smoke a cocktail
Smoke is aroma, not flavour. Applied well it transforms a spirit-forward drink; applied too freely it turns it into an ashtray nobody wants a second sip of.
Smoking has become the favourite visual flourish on modern menus, which is exactly why it is so often done badly. The key is understanding that the smoke is not there to flavour the liquid, but to fill the space between the surface of the drink and the drinker's nose with aroma.
Three ways to do it
A smoking gun with a cloche or an inverted glass is the most controllable. You generate the smoke separately and decide exactly how much goes in and how long it stays. It is the option if you plan to smoke regularly.
A burnt wood chip under an inverted glass costs nothing and works just as well. Light the chip on a heatproof surface, cover it with the upside-down glass and wait for it to fill. Then flip it over and pour the drink in.
A torched garnish is the subtlest: a singed rosemary sprig or a flamed orange peel. It does not smoke the drink, it perfumes it. In many cases that is exactly the right dose.
How much is enough
Ten to twenty seconds of contact. The glass should be left with a faint veil, not opaque. If lifting the cloche releases a billowing cloud that takes a while to clear, you have overdone it and the drink will taste of ash.
Smoke the empty glass, not the liquid. Alcohol absorbs smoke compounds unevenly and very quickly, and once they are in there is no going back. With the glass, the aroma clings to the walls and releases gradually as the drink is consumed.
Which wood to use
Cherry and apple give a sweet, gentle smoke that suits agave and rum. Oak and hickory are far more intense and can stand up to whiskey. Never use resinous woods like pine: the smoke turns bitter with a turpentine edge.
Safety
Always work in a ventilated space and on a heatproof surface. Keep the flame away from open bottles: high-proof alcohol vapours catch easily. And before putting anything away, make sure the embers are completely out.