Small bracket ID

[RobSutton]

Any ideas about this one - I came up with two possibilities using Roger Phillips - one was a Trametes either hirsuta or gibbosa the other was Postia subcaesia but I'm not convinced by either. Growing on a dead Birch (Betula pubescens) Cap c5cm across doesn't seem to be hairy, the pores are very small and seem to be nearly circular near the margin but more elongate further back. The smell is "fungusy" and there doesn't seem to be any particular taste.