(I,m a newbie fungi-hunter so am just getting to grips with identifying fungi and how to post on here - please forgive me if I've got it wrong!

)
I found these fungi growing on a low oak stump right next to a main woodland path (an old railway line, to be accurate). There were several of them, varying in size from about 5cm to 15cm. I haven't been able to identify them so far.
Cap: centre is off-white, remainder is grey/brown mottled.
Gills: creamy-white, adnate, bruise to crimson or brown (seemed to differ in 2 specimens).
Stem: creamy-white, off-centre and rounded but tapering slightly towards cap.
Can anyone help me identify them, please?
Thanks
Sneezewort