Jules-

for all i can tell the Plasmon-cookies that Twain not only ate but
apparently also tried to market in the States are more or less in the
original form still available from the surviving Italian branch of the
company. I am attaching a pic of the box. Couldn't find a proper address,
but they seem to belong to the Heinz multinational octopus ...
During the late 19th c., many companies were trying to sail in the wake of
Justus Liebig's Fleischextrakt broth-cubes, so gruesome stuff like "Torpon"
(made from offal and other meat leftovers from slaughterhouses) got on the
market ... Nutritionally enriched cookies and other foods were also
experimented with. "Plasmon" seems to be / have been edible, but the company
branch in the US apparently collaped through mismanagement:
http://www.twainquotes.com/19071221.html.

Hope this helps -

wolfgang

Prof. Dr. Wolfgang Hochbruck
Albert-Ludwigs-Universität Freiburg