Greg Henry describes the Tartufo cocktail, which can be found in his book: “This cocktail seems fresh and light at first glance, but behind all those bubbles and bright botanicals there’s a dark earthiness. It comes from truffle-infused honey, available in most good cheese shops, at gourmet markets, and online.”
* Combine black truffle honey and warm water in a 1:2 ratio.
Stir together the gin, lemon juice, and honey syrup in a cocktail shaker, making sure the honey dissolves completely. Slap 1 rosemary sprig between both of your hands, or gently pinch it all over to release the oils, and add to the shaker. Fill the shaker 2⁄3 full with ice; cap and shake vigorously until the cocktail is well chilled. Using a Hawthorn strainer, double-strain through a wire-mesh sieve into an ice-filled highball glass. Top with club soda and stir gently. Garnish with the remaining rosemary sprig.