Hazel Bracket - Skeletocutis semipileata

Resupinate or forming brackets, usually on Hazel branches, with whitish to brownish upper surface.  The fertile surface is white to cream and has very small round pores.  It causes a white rot. 

Taxonomy is difficult, and this may be a complex of species including S nivea, S nemoralis and other species; microscopic examination may be needed to identify with certainty (ref:.https://www.gbif.org/species/10136541) 

Photograph upper- and under-side of bracket, and in situ on host plant.  You must ensure you have identifed the host species correctly.

Hazel or other deciduous tree