Great caramelized onions require slow cooking over medium heat. It takes an hour or more, but the time spent is worth it if you’re looking for a great topping for burgers or pizza.
Recipe from Bon Appétit.
- 2 large yellow onions, peeled (about 1 lb.)
- 2 Tbs. unsalted butter
- Kosher salt
- Low-sodium chicken broth or water, optional
Halve both onions through root end. Using the tip of your knife, cut a V-shaped notch around root to remove it (this will ensure that all slices separate when you cut the onion).
Place 1 onion half on your cutting board so root end is facing you, then thinly slice onion lengthwise, starting at one side and working all the way to the other (so your knife runs through the root halfway through, not starting or ending at the root end). You’re going for slices that are 1/4- to 1/8-inch thick.
Repeat same slicing procedure for remaining onion halves.
Heat 2 Tbs. butter in a large saucepan over medium until melted and sizzling. A pan with high sides will keep the onions from flipping out onto your stove. Using a pan that also has a wide base gives water room to evaporate, allowing the onions to caramelize rather than steam.
Instead of dumping in all of the onions at once, which would fill the pot and make it hard to stir (which would then cause the ones on the bottom to cook faster), start by adding just a couple of large handfuls to the pot. Cook, stirring, until onions are soft and starting to turn translucent, 1 to 2 minutes. Stir in a few more handfuls of onion and repeat cooking and stirring process until you’ve added all the onions. Season with a pinch of salt.
Reduce heat to medium-low and continue to cook onions, stirring every few minutes to prevent them from sticking and coloring too much in any one place, until blonde-colored, 15 to 20 minutes (the point of doneness for French onion soup). If you feel like onions are getting too brown around the edges or they’re sticking, reduce your heat a bit.
If you’re going for onions that are softer and more caramelized (for a patty melt or onion dip), keep cooking, stirring on the regular, until onions are unmistakably golden brown, another 15 to 20 minutes. Because most of the water has cooked off at this point, there might be some bare spots where the pot could start to burn. If this happens, stir in a splash of broth or water. The liquid will dissolve the cooked-on bits, which the onions will re-absorb.
For extra-dark onions, the kind that make a great burger topping, cook until they start to almost blacken around the edges and go slightly crisp, another 10 to 15 minutes. This requires constant attention so they don’t burn.
Let onions cool in the saucepan, then use or transfer to an airtight container and chill. They will keep up to 1 week.