When ye olde tavern keeper asked his patrons, "What's your poison?" their answer may very well have been, "Posset, please." The warm, creamy forerunner to eggnog was "all the rage in the late Middle Ages," according to The Glutton's Glossary, by John Ayto.
In Shakespeare's Macbeth, the poison was more literal—Lady Macbeth slipped a couple of Mickeys (or their contemporary equivalents) into the possets of the guards outside Duncan's quarters so they wouldn't get in her murderous way.
I must have passed over that mention of possets during my college reading of the play—dismissing it as just another unfamiliar word among many—because I didn't recognize it when I next saw it, at the Shelburne Museum, in Vermont.
During a visit there last summer, I was intrigued by a some elaborate looking vessels in the collection. They resembled large, two-handled teapots, but the labels identified them as posset pots. Posset pots, made of ceramic or metal, were specifically designed for the job: since posset was both a drink and a dessert, with a layer of thick, sweet gruel floating above the liquid, the spout allowed the liquid part to be drunk separately from the thick layer, which was eaten with a spoon. The pot was often passed around at English weddings to toast the bride and groom. In an exhibit called "Design Rewind: The Origins of Innovation" a couple of years ago, the museum compared the posset pot's design to the modern-day toddler's sippy cup.
Posset recipes varied widely, but they usually contained wine or beer, cream, sugar and egg, and were thickened with bread, biscuits, oatmeal or almond paste, which formed the top layer. One 17th century recipe doesn't make it sound too appealing:
Take a quart of thick cream, boyle it with whole spice, then take sixteen eggs, yolks and whites beaten very well, then heat about three quarters of a pint of sack , and mingle well with your eggs, then stir them into your cream, and sweeten it, then cover it up close for half an hour or more over a seething pot of water or over very slow embers, in a bason, and it will become like a cheese.
I can't imagine that a beverage being "like a cheese" would ever be a good thing. We may have hit upon the reason why possets have all but disappeared from the winter beverage scene.
In Britain, the word posset has made a comeback, though it now refers to a light, creamy dessert, similar to a syllabub. And what's a syllabub, you ask? A creamy drink or dessert made with wine, sweetened cream and sometimes beaten egg whites. As for the silly name, The Glutton's Glossary informs, "that remains a complete mystery."