Someone help identifying this mushroom please

[Helder]

Hi, I have found this mushroom growing on a line on a moist forest floor on leafs and dead wood. The cap is up to 15cm diameter and a greyish brown, darker in color in the middle and convex when young. The gills are a very pale yellow and attached to the stem which is just slightly bruising brown at the bottom. White flesh, doesn't stain. It smells delicious and fresh. Found in Laurissilva forest in Madeira Island. (Europe/Northern Africa). This one has been really hard to identify for me. Any help is appreciated.

[Dave W]

Knowing spore print color would help here. Collect a print on a non-absorbent white background (and also black). If enough spores fall onto the white surface, you will be able to tell if the print is white or some pale shade that's slightly different from white. On the black surface you can tell if any spores have fallen. My assumption here is these mushrooms have pale spores. 

Another thing to check is whether or not the layer of gills may be easily peeled off of the rest of the cap. If the gill layer peels/slides easily off, then these may be a species of Leucopaxillus. Mushrooms in this genus have white spores.

Another genus of white-spored mushrooms to consider here is Melanoleuca.

Mushrooms representing species of genus Clitocybe have spores that are white, pale yellow, or pale clay-colored. Clitocybe mushrooms usually have gills that are decurrent, similar to what is seen in the photos. That is, the gills are attached to the stalks running down thee stalks. Some Leucopaxillus mushrooms also have decurrent gills.

Another genus to consider is Lepista. These mushrooms have pale pinkish/tannish spores. 

Lots of possibilities here. These mushrooms may be a species that I don't see here in eastern North America. There's a strictly European large white-spored mushroom that begins to appear in some Mediterranean areas during March, Calocybe gambosa. The gill attachment for C. gambosa is reported as "sinuate", meaning the gills are tapered and only thinly attached to the stalk. The gills seen in the photos do not appear to be sinuate. 

IDing tricky gilled mushrooms like these often requires using a microscope.