Help identify a strange root vegetable The other day I ventured into a grocery store that sold a lot of root vegetables that I have never seen before. 

One of the vegetables was a large round thing, and when I poked it, grey 'smoke' came out of it, like one of those mushrooms you stepped on as a kid. None of the vegetables were labeled, so I don't know its name. 

Does anyone know if such a thing exists, and what does one do with it?
Are you sure it was not in fact a puffball fungus?  There are some varieties that are edible and can be found in grocery stores.  Depending on how fresh, and when they were picked, they could easily be mistaken for a root vegetable.  Look for pear shaped puffball here for an example. http://www.wildernesscollege.com/edible-wild-mushrooms.html