[mannerheim]

It isn't really possible to prepare beef in a way to eliminate prions; you have to just make sure the beef you're preparing doesn't have them.

[incrudible]

I'm aware that prions are hard to destroy, but that's a different question as to whether they are contagious. A lot of contaminated beef did enter the food chain, yet the expected surge in vCJD did not occur. I would expect cooking to have some impact here, but that's just a guess.