Found and identified by Else Vellinga. Mike Wood created another observation of the same specimen.
For those not familiar with the genus, according to Else Vellinga, Flammulasters are small brown or very pale brown spored mushrooms growing on vegetal debris and wood, typically with a flocculose cap cuticle made up of round cells.
I also found the following reference for those who want to know more:
Vellinga E. C. 1986 The genus Flammulaster (Agaricales) in the Netherlands and adjacent regions. Persoonia 13: 1-26.