First, peel your onions and slice them thinly. I like about ⅛- to ¼-inch thick slices — thin enough to break down well, but thick enough to hold some texture.
Choose a large, heavy-bottomed pan . Add olive oil, butter, or a combination of both over medium heat. When the fat is hot and shimmering, add all your sliced onions.
Cook over medium to medium-low heat, stirring every few minutes. At first, the onions will soften and turn translucent. After 10–15 minutes, they’ll start to lose volume.
Add a pinch of salt at this stage. Salt draws out moisture, helping them break down. If you want, you can also add a pinch of sugar to help speed caramelization and intensify the sweetness
If the pan gets too dry, splash in a tablespoon or two of water, broth, wine, or even balsamic vinegar and scrape up the browned bits
Real caramelized onions take at least 40–45 minutes. Some cooks go for an hour or more for deep, dark, almost jammy onions. They’re done when they’re deep golden brown, sweet, soft, and taste so good you want to eat them by the spoonful.
