Other than tasting distinctively delicious, onions are high in vitamin A and have been documented to inhibit the formation of blood clots and to lower blood pressure and cholesterol levels. Interestingly, the scent of whole, unpeeled onions is rather benign but as soon as the flesh is severed, amino acids react with other enzymes to produce a sulfuric acid that gives the onion its pungent scent and robust flavor. And the older the onion, the stronger and more assertive these compounds become. But pungent doesn’t mean “foul”; a bad smell indicates a bad onion that should be bypassed in the market or discarded at home. Fortunately, during cooking, onions go through a chemical change that leaves them incredibly sweet and savory.
To buy onions: Look for those with a thin outer skin that feels like dry crackly paper. The neck of the onion should be closed tightly with no signs of sprouting, mold or soft brown spots. As a general rule (but this will vary with area), white onions tend to be stronger than yellow or red onions. Reds are usually eaten raw, and yellows are the best choice for an all-purpose onion. The huge Spanish onions are my personal favorite for their consistently sweet taste, especially after cooking. And now, a slew of spring and summer hybrids are being bred primarily for sweetness. These varieties (Vadalia, Walla Walla, Maui Sweet and Italian Sweet) should be eaten raw to enjoy fully their intense flavor.
To store onions: Store onions loose in a dark, dry bin with plenty of space around each to prevent them from sweating. And although onions and potatoes are a match made in heaven when cooked, don’t store them raw in the same bin since both emanate moisture and gas that cause each other to spoil. If you have leftover cut onions, store them in the refrigerator tightly wrapped in plastic wrap and use them as soon as possible to prevent drying and an “off” scent and flavor. Chopped onions can be frozen, if desired, but they tend to become somewhat wet and translucent after thawing; they’re fine for sauces, but won’t brown well.
To stop those tears: Regarding those handed-down secret tricks to keep you from crying elephant tears when chopping onions, I inevitably just squint and whimper through the entire process. Chilling the onion before cutting helps somewhat. Although many suggest running them under water, I have found that it adversely affects the color and texture of the cooked onions. (I don’t chop onions in the food processor for the same reason unless their ultimate use will be as one component of a minced vegetable base for certain sauces.) The best remedy is to learn to chop more efficiently so that your crying time will be reduced. Sorry, it’s the best trick I have.
To chop onions: The secret to chopping an onion is to keep each half intact at the root end until you complete the final (third) slicing. Using a well-sharpened 8- to 10-inch chef’s knife, trim off the pointed top and remove the outer papery skin, but leave the root end intact. Cut onion in half lengthwise through the root end (not through the round middle). Working with one half at a time, lay it (flat side down) on your work surface. Hold onion in place with one hand and position your knife so it’s parallel to the cutting board, about 1/4 inch above the bottom. Starting at the bottom, drive the knife through the onion in a sawing motion until you reach 1/2 inch from the root end. Ease out the blade, reinsert it 1/4 inch up from the preceding cut, and follow the same procedure. Repeat until you reach 1/4 inch from the top. Next (with the onion in the same position) point the knife blade down and make vertical lengthwise slices 1/4 inch apart from the top to within 1/2 inch of the root end (grasp the onion with your other hand as you do this so that it stays intact.) Finally, starting at the top, slice crosswise at 1/4 inch intervals until you reach the uncut root end, releasing small diced pieces onto your work surface. Turn the uncut portion flat-side down, slice off and discard the root end and make horizontal, then vertical cuts as described above. If a finer texture is desired, use the knife to go back and forth over the onions in a smooth rhythmical motion.
To mince onions: Follow the preceding procedure for chopping onions, but make incisions 1/8 inch apart.
To slice onions into thin strips: Cut the onion in half, through the root end and cut off the roots. Working with one half at a time, lay the onion on it’s round side and, starting from the center and working toward the outside, cut the onion into very thin wedges. When done, separate the wedges into thin strips.