Phylum: Basidiomycota Family: Fomitopsidaceae
Fomitopsis betulina (Bull.) B.K. Cui, M.L. Han & Y.C. Dai
Birch Polypore; Birch Bracket
Also known as the Razor-strop Fungus as the cap surface has been used to sharpen razors. Very common wherever ageing and decaying birch is found. An annual species but old fruitbodies can be found decaying into a second year
References:
O'Reilly - Fascinated by Fungi;
Ryvarden & Melo - Poroid Fungi of Europe