Just checked with Dan Lindner at the Forest Products Lab. Here's his response:
"It's Pisolithus tinctorius (Dead Man's Foot), which is well known for breaking through pavement and driveways. It really likes compacted, sandy, gravelly soil. It's is an important mycorrhizal species (sometimes used in forestry operations to inoculate seedlings). It is generally not considered edible, which shouldn't be too surprising."
Hope this helps.
Brian (:))
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