I think I posted a link to that study, yesterday.   When you speak of the
'Persian' walnut I assume you are speaking of Juglans regia vs. Juglans
nigra (black walnut).     Juglans nigra is the native tree to the area of
Italy where it is made so while it would be an interesting experiment to
compare the two,  the black walnut  is traditionally used.  

The original recipe for nocino as a beverage,  I mentioned yesterday is the
recipe from the Italian organization I linked to. The claim being that  it
is a translation of  a manuscript that group has access too.     It was so
old as to be common knowledge by the time Tusser and Hugh Platt were copying
down older recipes.  I don't think much of those two as they plagiarized a
lot of older sources for their information, but I have to grudgingly admit
that most medicinal texts of the period were just reworked versions of old
Greek sources.    

There is mention of a medicinal made of walnut in the Herbarius Apuleii.
Culpeper mentions the "green young nuts taken before they be half ripe and
preserved with sugar are of good use for those that  have weak stomachs "
The process of preservation would have involved spirits as well but he
doesn't specify a recipe because that process was such common knowledge at
the time.  But that at least give you a reference to document the use of the
walnuts as a digestif, even though it isn't specifically referred to as

I will be interested in what you think of the preparation made with the
Juglans regia.