One of the most famous cocktails in the world, no other drink has such a hold on popular culture as the Martini. Its simplicity—made of just gin and vermouth, chilled and served up—belies a thousand different ratios and iterations, hotly debated in cocktail culture. This Saturday, Julian and Mary Francis will host a seminar in how to prepare, modify and enjoy the classic drink that journalist H. L. Mencken famously declared to be “the only American invention as perfect as a sonnet.”