Chestnut mushroom
From Cookipedia
Chestnut mushroom, Poplar mushroom, Velvet pioppino (Agrocybe aegerita, also called Agrocybe cylindracea or Pholiota aegerita), is an edible fungi that is commercially cultivated for human consumption. They have a marginally better flavour than the similar white mushroom. If left to grow larger thay are similar to the portobello mushroom only with a tan coloured cap.