Real eggnog is a 20% ABV custard punch, not carton goop—George Washington served his with rum, sherry, brandy, and whiskey. Born from medieval posset and revived by craft cocktail bars, eggnog’s rum-vs-bourbon-vs-brandy and fresh-vs-weeks-aged battles come down to technique: violent shaking to emulsify raw eggs, whole milk + heavy cream, and fresh-grated nutmeg, with the booze preserving (and smoothing) over time.