The cap can grow up to 2 ½″ wide (6 cm) and becomes very flat when fully mature. The centre of the cap is brick red, then shades to yellow toward the edges, becoming brown around the edges.
The mushrooms need to be harvested young. When young, the cap will be more curved on top, and have pale tan gills underneath. As the mushroom matures, the gills turn grey.
The flesh is firm with a mild flavour.
Brick Top Mushrooms are sometimes also called Cinnamon Cap, because an American distributor of mushroom spawn has unfortunately decided to start calling them that, whereas previously Cinnamon Cap was used as an English name for Nameko mushrooms.
Brick Top Mushrooms are very popular in Japanese cooking. They can be grown and bought commercially.
Sources
University of Wisconsin Green Bay. Biodiversity of Macrofungi in Northern Door County, WI. Accessed December 2015 at http://www.uwgb.edu/biodiversity/resources/mushrooms/descriptionsI-N.asp