Phylum: Basidiomycota Family: Physalacriaceae
Flammulina elastica (Sacc.) Redhead & R.H. Petersen
There are few British records but many may have been misidentified as the very similar to Flammulina velutipes. F. elastica has larger spores and is predominantly found on willows Salix
References:
Knudsen & Vesterholt, editors (2012) Funga Nordica