By - LuckyPQ
Looks like it could be in the Agaricus family. I found something similar but mine was much much smaller.
Yes, agreed it's an *Agaricus*
Maybe A. Auricolor but not sure if they can be so small and so big at the same time. Well this is Netherlands so probably not.
Maybe Lepiota brunneoincarnata?
It has dark gills. See 2nd picture