The parable of the rabbi from Kiev, Yom Kippur and the half-eaten bar of chocolate

Now that another Yom Kippur has been and gone without my being struck down for my sins – the biggest of them, in some eyes, being my failure to honour the Day of Atonement in the way a Jew is supposed to – I will unfold to you a tale. Call it an expiation for not adequately expiating.