1970s/80s
Large single biscuit sold in clear cellophane. About 3/4 times bigger than a normal round biscuit.
It was round shaped but had a wavy edge.
Top was milk chocolate and the bottom was shortbread like, not actual shortbread I don't think, but similar. Sugar sprinkled on it.
I'm getting the word Chesthunt but can't find anything on Google.
At that time I was living in London/Essex and they were sold in most supermarkets.