Ah ha! I knew rosin baked potatoes had been discussed before here, but
it was *many* years ago:

http://bigspud.com/files/pbakedresin.htm

I just happened to be flipping through a cookbook called 'Bayou
Cuisine'. (It belonged to my mother, probably given to her. She wasn't
particularly interested in cooking.)

Anyway, it says to melt 10-15 lbs. of rosin/resin in a deep cast iron
kettle. When melted and bubbling lightly drop in potatoes of medium to
large size. After 45 minutes to an hour the potatoes rise to the
surface and are cooked another 15 minutes. Remove with iron tongs and
place on a piece of heavy butcher paper, or newspaper, which is twisted
around it to form a jacket. Cut through the paper and potato and serve
it topped with butter, salt & pepper.

So, they aren't really "baked", they're boiled in pine rosin/resin. I
remember having one of these "baked" potatoes these *many* years ago at
Cracker Barrel.

I wouldn't have any idea where to buy pine rosin/resin if I were so
inclined to make something like this. Still, it's an interesting
cooking concept.

Jill