Where is the Fleur de sel used?

Salt is in step 6. I agree with Nancy. Fleur de sel is great if you have it, but any coarse salt will be fine.

A delicious but/and expensive regional sea salt from France (Britrany, if I remember right).
Usually applied to any food as a garnish after cooking of just before serving.
Same with caramels.
But this recipe only calls for very small amount so, if not avaliable, you could replace it with another good sea salt or flakes of kosher salt.