Rim a chilled old fashioned glass with lemon and dip into lemon/rosemary salt.
Place prepared glass over the charred rosemary sprig in order to trap the fragrant smoke in the glass.
Mix all ingredients over ice and strain into prepared glass.
Garnish with the charred rosemary sprig while still smoking.
The smokiness of the tequila and mezcal blends well with the other herbal and flowery notes provided by the Chartreuse and St. Germain, while the lemon juice and agave lend a subtle sweet and sour note. The charred rosemary and Eau de Vie of Douglas Fir round everything out with a sharp bracing astringency.