Pam Moore wrote:
You don't say on soil WHERE.

Underneath one of my butternut squash plants!

You don't say how BIG.

About what I would consider Mushroom Size. So ... 2" stem, relatively thin
parasol top

Look up parasol mushroom on Google images.

Yeah, tried that first, didn't look anything like any of these
http://en.wikipedia.org/wiki/Parasol_mushroom#Gallery

It sounds a bit like it, but there are so many similar things.

I think it was the first one I tried. :-)
Of those photos, first is too pointy, this one was rounded. They all are
too 'bitty' on the top. The last is way off colour.

Parasol is a delicacy and one I would eat.

I am /incredibly/ mushroom-phobic for anything other than shop-bought or
where I've grown myself from known spores. I probably died of mushroom
poisoning in a previous life.