Visit beFOODled on Flickr.Update: If you make this recipe you should cook fiddleheads for longer than I did, because it seems they can make you sick if they aren't well-cooked. Health Canada recommends that "fresh fiddleheads be cooked in boiling water for 15 minutes or steamed for 10 to 12 minutes until tender. Water used for boiling or steaming should be discarded as it may contain the toxin.