Unknown fungus

Found this growing under the vegetable netting between peas and cabbage, it's at least 6 inches across but I don't know what it is.
Mostly dry today so I managed to get caught up with the washing, pick plums, do some dead-heading in the garden and do some of the mosaic.
I also had my evening run with the group, though that wasn't dependent on it being dry. We did avoid the woods, though, after yesterday's rain.