Martin Luther, who grew up in cramped conditions among six brothers and sisters, wrote about his parents’ house that it was very strict. Even negligible failures and lapses were punished severely. One day, Luther’s mother found a nut in Martin’s pocket. She chastised him, so that even on the next day there were bloody wales on his back.
According to stories of that time, walnuts were pealed directly after the harvest and simmered in plum butter, to be served as a delicacy on special occasions. It must have been such a simmered walnut that Martin had in his pocket.
Konditorei Schmerker, a pastry shop in Worms, has created a praline from a walnut marinated in prune butter and glazed with a fine layer of chocolate.
(source: Rudi H B Schönbrodt)

If I am refuted neither by the Scriptures nor by clear reason; for
neither do I solely trust in the Pope nor in the Councils, since it is
obvious that they have often been mistaken or contradictory in what
they said, and so I am convinced by the passages in the Bible which I
have cited, and my conscience is captive to the Word of God. Therefore
I cannot and I will not recant anything, for it is unsafe and impairs
beatitude.