Phylum: Ascomycota Family: Lachnaceae
Lachnum fuscescens (Pers.) P. Karst.
Also known as Brunnipila fuscescens, it's very common on beech leaves and cupules
Læssøe, T. & Petersen, J.H. (2019) Fungi of Temperate Europe, Volume 2
Ellis, M.B. & Ellis, J.P (1997 new enlarged edition) Microfungi on Land Plants: An Identification Handbook