Doesn't your Fleur de Sel have a little note on the side about how it's got all the minerals of the sea in it? (I paraphrase, of course). You can use that, perhaps, as a menu note. Put that the chef cooks solely with Fleur de Sel and here are its qualities.
At least *some* of your customers will have their eyes opened. It's not easy educating people, keep that in mind!
Next, you can start cooking with Virgin Coconut Oil! ;-)