The chocolate bismark is a species of Berliner doughnut, available in certain locations throughout southern Wisconsin, for example, here.
I have fond memories of the bismark. As a boy of 13, I delivered the morning Wisconsin State Journal newspaper. One of my customers was a now defunct "micro-bakery," run by an old Bavarian woman. Each morning around 6 o'clock when I stopped by to deliver the news, she would treat me to a freshly baked chocolate bismark. They were especially tasty and appreciated in the dead of winter.
Real chocolate bismarks are becoming hard to find, having been displaced by custard-filled species, and also by bismarks prepared with a lighter-colored dough. I googled around looking for a photo of the real thing, but to no avail. The photo above is the real deal from my trip back. Accept no substitutes.