A posset | The Oxford Companion to Spirits & Cocktails

is a drink made from curdled milk or cream and wine, fortified wine (such as sack), or ale, the mixture being warmed, sweetened, and frequently thickened by the addition of eggs or egg yolks, bread, oats or barley, or pounded almonds. Left to set, the posset separates into layers—the light and foamy “grace” rising to the top, a custard-like middle layer, and the alcohol below. The upper layers can be eaten custard-fashion with a spoon, leaving a bottom layer of warmed, spiced, or sweetened drink. See layering. Posset originated in medieval Europe as a quasi-medicinal beverage, and its construction became more formalized by the sixteenth and seventeenth centuries. “Posset pots” of this period—typically of earthenware or metal—came with a built-in straw that allowed the liquid layer to be sipped from underneath the topping. This cream-on-top/liquor-below arrangement suggests that the posset is a close cousin to the unheated Syllabub, if plainer, although it is undoubtedly fancier than another cousin, the gruel-and-ale caudle.The precise definition of the posset proves mutable and nearly infinite in variation. The English cavalier and natural philosopher Sir Kenelm Digby’s 1669 recipe for “Sack Posset” is particularly dependent on eggs for body, calling on “half a pint of Sack, and as much Rhenish wine” to be sweetened with sugar, beaten with no fewer than ten egg yolks and eight egg whites, and heated with cinnamon, not to boil but to thicken. Three pints of sweetened cream are boiled and added to the wine and eggs, then the whole is heated, with lemon juice sprinkled atop, and “if you will, you may strew Powder of Cinnamon and Sugar, or Ambergreece upon it.”

As late as 1750, the posset in its plainest variation can take the form of a workingman’s meal, as in Hertfordshire farmer William Ellis’s “palatable supper” of a posset “crum’d with bread” in combination with stale beer and fresh milk. In Shakespeare, posset is largely a pre-bedtime drink or nightcap; in Macbeth, Duncan’s guards have theirs “drugged” by Lady Macbeth, while in The Merry Wives of Windsor, Mistress Quickly promises to make Jack Rugby a posset “soon at night, in faith, at the latter end of a sea-coal fire.” Yet posset could also be a fashionable drink served with ceremony: Queen Mary I and her husband, Philip II, received an elaborate crystal posset serving set as a betrothal gift in 1554.

The posset was effectively obsolete by 1800 and, unlike many other such drinks, has not been successfully revived by modern mixologists.