Restrictive vs. Non-restrictive Elements Answer 3

Going on a treasure hunt in the desert with Juliette Binoche which has always been a fantasy of mine seems out of the question.

Answer:

Going on a treasure hunt in the desert with Juliette Binoche, which has always been a fantasy of mine, seems out of the question.


Commentary:

In this case the clause "which has always been a fantasy of mine" does not refer back to any specific noun at all. It is purely additional/parenthetical information. Therefore, it must be set off with commas.