The Ladies Best Companion; Or, a Golden Treasure for the Fair Sex. Containing the Whole Arts of Cookery … With Plain Instructions for Making English Wines, Etc (1800)
Pickled walnuts is a common pickled side served in England most commonly with cold meat and blue cheese. Its believe this delicacy, which would not be amiss on a charcuterie board, originates sometime in the 18th century but that is largely based on written mentions in books and stories.
There are many modern recipes available for those aiming to try this treat, or it looks like a premade version is widely available in the UK or for export.