Caramelized onions are a great “secret” ingredient to have on hand. They lend their deep flavor to so many dishes, like roasted chicken or mashed potatoes or pizza. But also to stews, sandwiches, burgers and more. The secret to making them is patience. It can take awhile for the onions to become deeply browned. Covering the skillet at the beginning helps the onions to soften and release their liquid, then slowly cooking them uncovered makes them meltingly soft and sweet. Since caramelized onions stay well covered in the refrigerator for a week, and can even be frozen, you may want to make a double batch to keep some for an instant source of flavor to enhance weekday meals. If you do that, use a 12-inch skillet to accommodate the extra volume.