How to identify it?
Fruiting Body
Fruiting body rather small.
Cap
Cap 1-3 cm across, fat conical at first, becoming broadly conic to convex, sometimes broadly bell-shaped, and sometimes convex with a flaring margin; grayish brown or gray; surface pruinose coating. Flesh thin, fragile, grayish. Taste slightly sour (acidulous).
Gills
Gills adnexed, whitish or pale grayish, nearly distant.

Scientific Classification

Phylum
Club fungi Class
Mushroom-forming fungi Order
Gilled fungi Family
Bonnet mushrooms Genus
Bonnets Species
Nitrous bonnet