Butterscotch is a kind of English confectionnary and flavour. I am not sure what it is, but according to the article, it contains brown sugar, butter and other things. The French wikipédia article names it Caramel Écossais (Skota karamelo) which sounds clearer, but other Wikipedia articles prefer the original English name.
About the pie part of the question. I am not sure if the translation should be adjective + noun or a compound-noun. The article for Apple pie uses Pomokuko.
Here is an example sentence:
Do you prefer cinnamon pie or butterscotch pie?