OK, so they aren't shittake's but these are huge mushrooms!! I left for work one morning and saw, what I thought was, a white plastic bag that blew up onto the lawn. When I got a closer look I realized that they were mushrooms...and they are getting bigger and bigger.
The first picture was taken on 8/31 where it measured about 7 inches...yesterday it was as long as my foot...and today it is about 11 inches. There are a few smaller ones, but the largest is in these pictures. We've nicknamed it 'The Carrier Dome".