That is not the actual blood from a bull splattered across the plate. It is a very famous Hungarian red wine known as Egri Bikavér or "Bull's Blood of Eger". It is typically a very dense full-bodied wine that pairs well with game and beef. I simply reduced the wine and threw it onto the plate in dramatic fashion.
I cut 1 inch filets out of the whole heart and marinated them overnight in olive oil, balsamic vinegar and some of the wine. I cooked them just as I would cook a filet mignon, seared on high heat to medium rare.
I served the filet with a very classic pairing of horseradish and bone marrow. I cooked some whole fresh horseradish root in stock and pureed it with cream and butter. And I roasted off some bones and scooped little pieces of the marrow out.