Fomes Fomentarius

Not quite a beret, but it comes close. This picture was sent to me by my good friend Bert, a cutting from a Dutch National Geographic Magazine. It triggered my interest and, looking for more information, found that these mushrooms (yes, that's what it is, a mushroom!) are quite commonly used in Eastern and Central Europe. 

I quote Wikipedia:

Fomes fomentarius (commonly known as the Tinder Fungus, Hoof Fungus, Tinder Conk, Tinder Polypore or Ice Man Fungus) is a species of fungal plant pathogen found in Europe, Asia, Africa and North America. The species produces very large polypore fruit bodies which are shaped like a horse's hoof and vary in colour from a silvery grey to almost black, though they are normally brown. It grows on the side of various species of tree, which it infects through broken bark, causing rot. The species typically continues to live on trees long after they have died, changing from a parasite to a decomposer.

Though inedible, F. fomentarius has traditionally seen use as the main ingredient of amadou, a material used primarily as tinder, but also used to make clothing and other items. The 5,000-year-old Ötzi the Iceman carried four pieces of F. fomentarius, concluded to be for use as tinder. It also has medicinal and other uses. The species is both a pest and useful in timber production.

Have a look here, at a most interesting web site.