Chewy, chocolate nougat inside a layer of chocolate covering. It's quite chewy and will take you a while to get through! It's a nice stretchy kind of chew though so need to worry about pulling your teeth out with it! Or you could freeze it , which makes it a load more brittle, and it shatters when you bite into it, kinda thing.
Like a lot of confectionery, it was invented in the beginning half of the 20th century, and named for the Charleston, which was a popular dance around that time. Charleston Chew was mentioned in the Simpsons episode: Lisa the Drama Queen, if you wanna check it out. Pretty cool.