Black garlic is a traditionally Korean speciality that is also becoming common in North America and Europe. While it may be simple to purchase prepackaged black garlic, it can be more rewarding to make your own at home. Once your garlic is ready, you can use it in all sorts of dishes such as pasta, hummus, pizza or stir-fries. Fermenting the garlic is a simple process but it does take a long standby time, so be prepared to wait a while for your black garlic to be ready.
Put as many whole, unpeeled garlic bulbs as you would like in your container. The container can be any material that is safe for the oven, and should be big enough to hold the amount of garlic you want to make.
Wrap the container with the foil. You should wrap it as tightly as possible to prevent any contaminants from getting in and to prevent too much garlic aroma from wafting out.
Place the tightly wrapped container in an oven set to about 60 degrees Celsius (140 degrees Fahrenheit). Many ovens can't be set this low, but if it is a gas oven it may be warm enough with just the pilot light on. If you don't want to leave your oven on for an extended period, you can also use a rice cooker set to "warm," a food dehydrator with all but one of the trays taken out, a plate warmer or a slow cooker. Just be sure that the temperature remains at about 55 to 65 degrees C (130 to 150 F) and won't shut off automatically.
Leave the container to ferment for 40 days. It is edible at 10 days, but to get the full effect you should wait the full 40 days. In that time, the cloves will have become a deep, inky black colour, and will be soft and spreadable and slightly sweet, similar to roasted garlic but much richer in texture.
Be sure to use firm, tight bulbs of garlic that are not peeling or spotted. Fermentation intensifies the qualities of the garlic, and to get the best result possible you should start with the best garlic you can find. In the long run, it will probably not work out to be less expensive to make your own black garlic unless you are making an extremely large quantity, due to the energy costs of leaving an appliance on for 40 days. However, it can be a fun experiment if you are not worried about the cost factor.
It can be dangerous to leave any appliance plugged in or your oven on for 40 days. Consider not actually turning the oven on but just fermenting your black garlic under the pilot light in your oven, as this may be warm enough but is less wasteful and dangerous. Make sure to keep any flammable materials away from plugged-in appliances.