http://12bottlebar.com/2010/12/buttered-beere/
Have you ever been drinking beer on a cold winter day and wished to yourself "I really wish this cold beer was hot...and had a stick of butter in it?" If so, this recipe is for you. Sounds a lot like a custard or an eggnog of sorts. I'm sure I'll whip some up in the depths of winter and report back.
Medieval Butter indeed!
http://www.harkavagrant.com/index.php?id=353