Volvariella surrecta

Volvariella surrecta, commonly known as the piggyback rosegill, is an agaric fungus in the family Pluteaceae. V. surrecta mushrooms have white or greyish silky-hairy caps up to 8 cm (3.1 in) in diameter, and white gills that turns pink in maturity. The stipe, also white, is up to 9 cm (3.5 in) long, and has a sack-like volva at its base. Although rare, the species is widely distributed, having been reported from Eurasia, northern Africa, North America, and New Zealand. The fungus grows as a parasite on the fruit bodies of other gilled mushrooms, usually Clitocybe nebularis....read more on Wikipedia.