Is this a shiitake mushroom?

There is an area of my garden mulched in wood chips.  I saw this mushroom growing there today.





A Google reverse image search matches shiitake, and I did rip up a whole bunch of shiitake mushrooms from the grocery store and toss them around that area last year, in the hope that I could start a shiitake patch.

Nevertheless, I am not even remotely an expert on fungi, so it could easily be some lookalike I don't know exists.

Can you tell what it is, based on those pictures?  If not, what other specific things should I look for, to confirm its identity?

Of particular note is that ring around the stem, with the sort of ragged bits hanging from it.  I haven't seen that referenced anywhere as a shiitake trait.  Is that something that can appear on shiitakes, or is it something that definitely means it's a different species?

Although the cap and gills do look remarkably similar to that of shiitake, the persistent ring on the stem indicates that you probably have a lookalike species. Typically, the veil on  a shiitake mushroom will disappear when they expand, not leaving behind a ring on the stem. The stems are also fibrous and darken as they age.

Also, I have been growing shiitake for 30 years now and I've never seen them grow on wood chips in a garden. Shiitake is native to Japan, Korea and China, where they are found on dead and dying trees, logs and tree stumps.  A few wild "escaped" populations have been found in Wisconsin, California and Washington, however. But my gut feeling is that you probably have something else.

Okay.  Thank you!  That's very helpful!  I'm thrilled to hear from an expert on this.  ^_^