A large white fungus with white gills that darken to a pale pinkish colour at maturity.   The cap may be smooth or with small scales, and the base of the stipe is bulbous.  It has a white spore print.

Agaricus species have pink or brown gills and brown spore-print; white Amanita species have a volva.

Photograph from top down and from side and underneath; note size and habitat.  It is helpful to note spore-colour from a print. 

Permanent pasture.

June to November.

Local

Local in Leicestershire and Rutland.

https://www.first-nature.com/fungi/leucoagaricus-leucothites.php