The garlic bulb is a really unusual plant. Each clove in the garlic head is actually a single swollen leaf, according to Harold McGee. Garlic’s strong taste and smell is actually a protection the plant evolved: when an animal bites into it, the strong taste is released, repelling the animal.
A whole garlic clove has only a mild taste and aroma, but when you cut into it, the enzyme alliinase is released from one part of the bulb and reacts with the compound alliin (a derivative a the amino acid cysteine) in another part of the bulb to form allicin, which has the characteristic garlic aroma and taste. Note that the plant evolved this defense to keep away animals, and garlic is actually quite toxic to dogs and cats: you should avoid letting any get into their food.
The alliinase enzyme is quite sensitive to temperature. Students of Professor John Milner at Penn State carried out a simple experiment where they placed garlic cloves in a microwave oven for one minute. While the garlic cloves appeared unchanged, analysis showed that the enzyme had completely disappeared after heating. They noted that other types of heating are sure to give the same results.
So this means that you need to chop the garlic before heating or cooking it, and that you should let the chopped garlic stand for a few minutes before adding it to the food you are preparing, to allow time for the enzyme to work to develop the flavor.
Garlic has much more sugar in it (fructose) than onions do, and is thus more prone to burning. Cook it at low temperatures when sautéing it, or add it directly to a liquid.
These two facts explain why dishes like Chicken with 40 Cloves of Garlic are so mild. The garlic cloves are never cut up: and the alliinase is destroyed by heating soon after the cloves are added to the pot.
Always buy fresh heads of garlic. Avoid the ones in little boxes, as they may be very old. You should also avoid bottled peeled garlic cloves in oil, as they are prone to develop botulism, according to McGee. And do not refrigerate garlic, which also will reduce the flavor.
When peeling garlic, you can use the simple rubber garlic peeler tube shown above, or you can use Jacques Pepin’s technique, and just cut a small slice from the root end of the clove. This will free the skin and it will just about come apart in your hand. You can also just crush the garlic and pick out the peel from the rubble.
And how do you get that garlicky smell off your hands? Rub them with salt and then wash as usual.