JT - ditto here :
Surprised to stumble across this. Looks as though it originated in England years ago. This fact deduced by the site name. vk
I wondered what the stone was for; and thought that the recipe may have intended that the stone would hold heat in for a while, after the fire was out (???)
But, here’s the ‘Wiki’ on the recipe (it’s apparently an old folk story):
http://en.wikipedia.org/wiki/Stone_Soup
Anyhow: the soup looks tasty and nutritious :-)
JT