Anyone who harvests edible mushrooms in the forest or in a meadow, cuts them to the ground with a knife (except when it concerns agarics, which have to be dug out). One cleans them on the spot.
There is a special pocket knife for this purpose, which is a compound tool, with a blade to cut off the mushroom stem and a boar bristle brush to remove soil and dirt; that brush may or may not be collapsible. On the back of the blade there are sometimes teeth to remove coarser dirt or, according to some, the outer layer of the skin (the 'cuticule') (1). [MOT]
(1) http://www.opinel.com/ (January 2021).