The recipe was first recorded by historian Charles H. Baker in his 1939 guide Gentleman’s Companion, which also introduced American audiences to the rye-based Remember the Maine. Baker was not a bartender by trade. In fact, he was a former merchant who traveled around the globe seeking out new experiences and drinks, which he documented in his book. One such adventure brought him to La Cucaracha Cocktail Club in Mexico City, where he happened upon the Mexican Firing Squad two years before the book’s publication. As Baker writes, he and his companion ditched their chaperones, “2 young Mexican caballeros whose parents mattered in official circles in Mexico.

“We were herded into fancy, rather dull places, served too warm drinks,” Baker continues. “And finally on 1 occasion we broke off by ourself, sought out this bar—where an aristocrat native oughtn’t to be seen!—ordered things in our own way.” Despite Baker’s description and the bar’s name, which translates to “the cockroach,” La Cucaracha was anything but a seedy dive: The cocktail bar was an emblem of Prohibition-era swankiness, with a menu of 40 classics that featured an illustration of a cigar-smoking insect in a tuxedo and tophat. In any case, Baker and his companion “almost became wrecked upon” the tequila concoction.

Baker’s version called for two pours of tequila, the juice of two small limes, one and a half to two teaspoons of grenadine or plain gomme syrup, and two dashes of Angostura bitters. The contemporary version of the cocktail, calling for a bit more grenadine, produces a sweeter drink. You’ll want to start with blanco tequila, the most agave-forward expression of the spirit, which blends seamlessly into citrusy cocktails. Lime juice brightens and grenadine slightly sweetens the mix with its tart, fruity notes. Opt for a high-quality bottle of the sweetener or make your own version of the pomegranate syrup. A hefty few dashes of Angostura bitters add depth and warm baking-spice notes to the drink. Some modern-day iterations of the cocktail call for it to be topped with club soda, but the classic is plenty refreshing without it—a fine replacement for your usual Margarita.

Reference : https://www.liquor.com/mexican-firing-squad-cocktail-recipe-5270686