I made this several years ago for an SCA (medieval/renaissance reenactors) dessert revel. It was my favorite candy from that feast. Traditionally, Panforte di Siena in one form or another fortified the Crusaders on their long journeys. While I have no documentation for this particular recipe, there is an interesting file on Compuserve in the Living History library showing Middle Italian texts and translations (by Baroness Viviana di Castelloza [Vian Lawson]) of chocolate recipes in A.S.F. Carte Bardi II A.116. [Good luck finding this today...] This recipe was downloaded from the Living History library on Compuserve (PANFORTE.TXT) which places it in the days prior to the internet. Today I would use white rice flour rather than cake flour as I eat gluten free.