- "The meat of the Greenland shark is poisonous when fresh because of its high urea and trimethylamine oxide content. However, when properly processed, it may be consumed safely.[3][4] "
https://en.wikipedia.org/wiki/Hákarl
The reaction quotes are intriguing,
"That's hardcore. That's serious food. You don't want to mess with that. That's not for beginners." · "awful", "like a jellied cube of ammonia" albeit "technically edible" · "reminiscent of "blue cheese but a hundred times stronger" · "like chewing a urine-infested mattress"