When the first autumn rains come it is time to head down to the secret mushroom site where Agaricus bitorquis can be found year after year.
For some reason, they seem to favour growing under she-oak trees. Quite often they are found fully grown but still buried, with just the top of the cap visible in the middle of a lump in the ground.
These mushrooms can grow very big. 150mm across is not uncommon and they are thick and fleshy with it. When cut, the surfaces bruise slightly red. This picture shows one I am holding in my hand to give some idea of size and shape.
When cut through, they show a reddish staining, as shown on this picture.
At my favourite site for bitorquis, there are several other edible mushrooms. In this picture can be seen some Coprinus comatus and an Agaricus arvensis, all picked at the same site and ready for the pan!
As a postscript, I have read that these are sold as supermarket mushrooms, though I have never seen the red staining so distinct as on the ones in the wild.