Misnomer: Pfeffernuss. What is this anise bark cookie?

That doesn't sound like any of the German cookies that I am familiar with. Springerle are not (or rather should not) be thin, and they are imprinted with designs--although they are flavored with anise. However, they do not have any fat in them-except for the fat in the egg yolks.

Take a look at this link and see if you think biscochitos may be what your grandmother was making. And if you do make them, go ahead and use lard--lard makes a huge difference in the texture of baked goods.

http://www.santafenewmexican.com/life/taste/deconstructing-a-new-mexico-original-the-biscochito/article_be5e5fce-32ff-5ef4-bedb-5824e0576d0f.html

I make some that are very thin and crispy. My recipe also calls for cassia, anise oil, lard, molasses, brown and white sugar. Does this sound familiar?

This is interesting… I'm not sure what you mean by rolled-bark cookie. Do you remember anything else about them (dark or light coloured; crispy, crumbly, dense or soft; from which German region … ) ?
In addition to Nancy's excellent ideas, there are a few more German holiday cookies that could fit what you are describing:
Schmalznüsse ("lard nuts"), made from a very crumbly dough of flour, sugar, lard (or in more modern versions a mix of butter and lard) and baker's ammonia; half of it usually tinted dark with a bit of cocoa. Shaped into walnut-sized rounds (like Pfeffernüsse) they get flat-ish and a crackly top after baking. Most recipes only spice them with vanilla or citrus zest, but it's possibly that one would add aniseed instead, especially before christmas.
The word "Pfeffer" means pepper, but in traditional baking recipes it often stands for all kinds of once exotic spices: another name for Lebkuchen (the German version of gingerbread) is Pfefferkuchen ("pepper cakes") and they are spiced with ginger, anise, coriander, allspice, cardamom and cloves, seldom if ever pepper.
There are also Anisplätzchen (or, depending on the region, Aniskekse/-laable: "anise cookies"), made of a sponge cake-like batter (eggs, sugar, flour), heavily scented with anise.
After piping small rounds you let them rest for anything between an hour and overnight: the surface should be dry to the touch before they are baked (at a low temperature, to keep them very pale and moist in the middle); they look very much like french macarons, including that little "foot".

Most traditional pfeffernusse recipes I know used butter, had multiple spices & make round or small - not rolled flat - cookies. they looked like nuts, didn't have them inside. Audrey - I don't know what recipe your grandmother was making. Maybe she had an unusual variant...suggest you look more in the rolled-bark or anise-cookie sections to find a similar recipe.