My grandmother used to make homemade butterfinger bars. She used peanut butter, chocolate, corn syrup and sugar.
So to mix up this flavor, one would start with the obvious ( peanut butter and chocolate ) and then experiment with EM to get the sweetness correct.
If one can take the PG though, Tasty Vapors Tastyfinger is so inexpensive that its not really worth a persons time to try to replicate it. A 36mg bottle and a doubler can last a very very very long time.