A sensational ingredient from Korea that caught on in the U.S. several years ago, black garlic is simply regular garlic roasted for days until it turns sweet and jet black, with a licorice-like flavor. Chefs Nick Balla and Cortney Burns of Bar Tartine in San Francisco gave us this recipe; they use the garlic in soups, stews, and vinaigrettes (it's sensational in their black garlic and lentil soup). You'll need a rice cooker with a "warm" setting for this; a slow cooker on any setting is too hot.
Put garlic heads in a rice cooker set to "warm" (about 140°). Cover (make sure the lid fits tightly; you may need to wrap it with foil) and heat garlic until the cloves are soft, black, and sweet, 4 to 5 days.
Make ahead: Keeps, chilled airtight, 6 months.
Servings Makes 3 heads (about 30 cloves)