Bet it All on Black Garlic Burger

Have you ever heard of black garlic?  Neither had I, until our obsession with Bob's Burgers started.  In one episode, Bob has entered a burger contest and most of the episode centers around his kids trying to track down the featured ingredient of his entry, the "Bet it All on Black Garlic" burger.

Literally: black garlic.
This burger was AMAZING (as if there was any doubt - I highly recommend this book).  Tangy, pungent black garlic sauce and melty mozzarella?  Yes, please.

I could eat the black garlic sauce on everything - and as a matter of fact, we did.  The recipe yielded way more than we needed for the burgers, so we used the sauce to dip our fries and roasted cauliflower.  Nom.

What's the weirdest ingredient you've ever put on a burger?