The Blackthorn (not to be confused with the Blackthorne, with an ‘e’) is a simple, brilliant low-proof cocktail that tastes almost like cold mulled wine. It’s named for the blackthorn berry – another name for the sloe drupes used to create sloe gin.
You’ll need a very good, very fresh sweet vermouth for this; Carpano Antica or Punt e Mes are great choices.