Contrary to 1 person's view, A lot of little hidden gems in Southeastern Wisconsin do place a dollop of butter on top. Unless of course the butter is dripping, you are not eating a butter burger.
The mushrooms and butter basting add wonderful flavor to this burger. These were a hit with my family.
I really like mushrooms in any dish, but I Actually enjoy mushrooms when finely chopped and added to these hamburgers. They created the beef so rich and tender! Certainly a recipe to repeat once again and once again!
It is my knowing, as a lifelong Wisconsinite and Culver's fan, that the BUTTER in a BUTTERBURGER does not refer to including a pat of butter, but rather, buttering the surface of the BUN and grilling it. There are no mushrooms IN the beef, either. If this is copycat. well, it isn't.