This looks like some kind of Ganoderma, but the yellow pore surface looks like none that I'm familiar with. Most have a white to brown pore surface, but I'm not at all familiar with which species grow in France.
Thank you very much Vitog, I forgot to write it on the thread : This one has been seen in Saskatchewan Too bad I haven't been taking a picture of the bottom. Well I've read that this mushroom had lots of good health properties
Thank you very much Frog, This is the real color and indeed it matches with Pycnoporellus fulgens Cheers