To create black garlic, inventor Scott Kim puts conventional heads of garlic through a month-long, high-heat fermentation process. Kim's company, Black Garlic Inc., claims that the process gives black garlic about twice as many antioxidants as raw garlic. I can't find any studies to confirm that, but I can vouch for black garlic's utterly unique taste and texture. The cloves are soft and slightly gummy, akin to dried figs. And the flavor is similar to roasted garlic, though the pungency is diminished (so much that you can eat it raw without it lingering on your breath for days; instructions on the package even suggest keeping a head or two on hand for snacking, but that seems like pushing it to me) and it boasts a molasses-like sweetness.
I first used it the other night in an spaghetti aglio e olio-type dish, dressing the pasta with little more than extra-virgin olive oil, salt, some crushed red pepper flakes, chopped parsley, and Parmigiano-Reggiano, so I could spotlight the black garlic flavor. I noticed that it's substantially different from unfermented garlic, and not necessarily interchangeable. I plan to try it in some Asian dishes next, or other dishes where its rich, deep sweetness will be welcome. I have a feeling it'll become a pantry staple before long.