Chaga is parasitic and grows exclusively on living trees.
The tree you have pictured appears to be rotting. Additionally, the mushrooms on that tree have a clear top and bottom. Although the coloration is similar, the picture above does not appear to be Chaga.
I will, however, do some research to see if I can find what fungus in fact is growing.
To be honest, I'm not sure we have enough information here to help you in this case. There are many different kinds of puffballs, some are edible, some are not. Depending on the age they will also vary wildly in their look and consistency, so this makes it even harder.
I can really only recommend two ways to identify mushroom:
Get a decent book
Buy a ...
Hard to tell from photo, but: "gills" look yellow which is wrong for a button /agaricus compestri . Do they have gills ? If they have a spongy matter and not gills they are likely some boletin . Usually found under conifers. If so, likely edible but not much flavor.