Think raw or grilled when you think of red onions. Though red onions are also good when simmered into a jam-like relish for meats, their crisp texture and mild flavor are really at their best when eaten raw. Marinating them briefly in vinaigrette (or other acidic bath) accentuates their bright color.

Sweet onions are regional specialties such as Vidalias from Georgia, Mauis from Hawaii, Texas Sweets and Washington Walla Wallas. Eat them raw in salads or grill them briefly to highlight their fantastic flavor.

Shallots are at home in sauces. On the assertiveness scale, these mild-mannered relatives of garlic are similar to white onions, but their flavor is more refined and complex. Shallots are most often minced and added raw to vinaigrette or cooked until sweet and used as the foundation of many classic and modern sauces.

The Cut Makes a Difference
After deciding which onion to use, you need to consider how to cut it, as this has a dramatic effect on the final texture. If you want the onion to blend seamlessly into the dish, mince it. For a little more presence, dice it. If you want it to be unmistakable, slice it.

When slicing, I use the distinction of cutting the onion “with the grain,” from root to blossom end, or “across the grain,” which creates rings or half-moons. When you cut with the grain, the onion slices hold together during cooking and retain their shape better.

Onions sliced across the grain release more moisture and lose their crispness faster. I exploit this characteristic when I make onion soup by cutting half of the onions across the grain (these partially dissolve and thicken the soup) and half with the grain (these give the identifiable onion texture to the finished soup).

Avoid bruising the onion, whichever cut you choose. A food processor or dull knife used to slice or chop through an onion will rupture more of the onion’s delicate cell structure, causing the release of more of its sulfur-containing amino acids. These come in contact with other enzymes in the onion, creating the compound that makes you cry and makes the onion taste strong.

Tailor the Flavor with Heat
Three basic ways to cook onions include sweating, sautéing and caramelizing. To sweat an onion is to cook it until it’s soft and translucent, but hasn't begun to brown. The purpose of sweating is threefold: It reduces the sulfur compounds (which softens flavor), it heightens the sweetness, and it softens the texture.

Sweated onions lay the groundwork for dishes like braised meats, rice pilafs or risottos, and white sauces. They lend a natural sweetness that can’t be created by simply adding sugar. Sweat onions over low heat and use only enough fat to coat the bottom of the pan. If you use significantly more fat, you’ll “smother” the onions, a related process usually reserved for béchamel (white sauce) and other sauces that are ultimately thickened with flour-and-fat roux.

Sautéed onions are cooked until they’re golden brown. They’re tender, but not as soft as sweated onions. Because they have a more resilient texture and a richer, sweeter flavor due to the browning, they’re great in dishes like vegetable sautés, pastas and soups.

To sauté onions, use high heat and a minimum of fat. Heat your pan before adding enough oil or clarified butter to film the bottom of the pan and then add the onions. Don’t cover the onions while you're sautéing. Covering the pan traps steam, and steam keeps the onions from browning.

Sweating + Sautéing = Caramelizing
Caramelizing onions creates a new depth of flavor. When the onions’ sugars caramelize, a complex chemical process produces more than a hundred new flavor compounds. Each has a color, aroma and taste that combine to create a unique, soulful flavor that permeates a dish unlike anything else. Caramelized onions add color and depth of flavor to brown stocks, and they make a flavorful topping for pizzas, bruschetta, steaks and chops.

If caramelizing had a mantra, it would be “take your time.” This is a process that does not happen quickly. Depending on the amount of onions, it can take upwards of an hour. But developing the flavor slowly is worth it; rushing may get you the color, but much of the flavor will still be undeveloped, and some of the onions will simply be burnt.

To caramelize, combine the techniques of sweating and sautéing. Start by sweating over low heat, covering the onions while they sweat to keep them moist and prevent browning. When the onions are translucent, take off the lid and bump up the heat moderately. Cook without stirring until the onions on the bottom start to brown. Then, stir occasionally until the onions are a deep, luscious brown. The thicker the onions, the lower the heat should be in the final stage of cooking.

If the onions ever start to look dry and appear to be browning too fast, stir in a little water to moisten them and dissolve the sugars that are burning.

For additional preparation and handling tips, visit www.onions-usa.org.

Chef Robert Danhi is a James Beard finalist and award-winning author of Southeast Asian Flavors. His agency, Chef Danhi & Co, specializes in menu and product R&D, sales and marketing support and educational and training programs for foodservice.