Like A White Stone, But No, Is A Moshroom Agaricus Bisporus

Agaricus bisporus is an edible basidiomycete mushroom native to grasslands in Europe and North America. It has two color states while immature—white and brown—both of which have various names. When mature, it is known as portobello mushroom, often shortened to just portobello (also spelled portabello or portabella). Smaller sized portobello mushrooms may be called portobellini or portabellini.

When immature and white, this mushroom may be known as common mushroom, button mushroom, white mushroom, cultivated mushroom, table mushroom, and champignon mushroom. When immature and brown, this mushroom may be known variously as Swiss brown mushroom, Roman brown mushroom, Italian brown, Italian mushroom, cremini or crimini mushroom, baby bella, brown cap mushroom, or chestnut mushroom.
A. bisporus is cultivated in more than seventy countries, and is one of the most commonly and widely consumed mushrooms in the world.