If you're a burger eater, then you know that caramelized onions transform any hamburger into something special. The sweetness of the onion contrasts nicely with the savory meat and cheese while adding an additional layer of flavor to your favorite sandwich or veggie patty. They go great with just about anything and are easy to make.
Best onions for caramelizing
The best onions for caramelizing are yellow and sweet onions because they are the most versatile and go well with a wide variety of dishes. Red onions are particularly great with hearty beef dishes and stews with red wine. White onions are great to serve at barbecues.
How thin should you cut the onions
Don't cut the onions too thinly, or they will burn and dry out before they caramelize. Cut them into slices about ⅛-inch (3mm) thick.
What color should the cooked onions be
There are basically three colors that caramelized onions can be. Depending on your preference, you can caramelize them more or less until they are either blonde, golden brown, or deep golden brown. They are all delicious in their own way, and texture and taste change with each color. The darker the onions, the softer they are and the more caramelized they taste. For burgers, I love them rich golden or deep golden brown.
How long does the caramelization take
It's a slow process and takes around 45-60 minutes for the onions to be fully caramelized, soft, and delicious. I don't recommend speeding up caramelization process by adding baking soda or increasing the heat.
Expert tips for success
1. Pan choice
I prefer a cast-iron skillet, but any non-stick skillet works just as fine. I recommend using a large pan between 11-12 inches (28-30cm) wide so that the steam from the onions can escape quickly. If using a small pan and therefore overcrowding the pan, the caramelization process will take a lot longer.
2. Butter and oil
I recommend using butter and oil for caramelization as oil has a higher smoke point and butter gives you great taste. Combining both is the best of both worlds - avoiding burning the onions and having great taste.
3. Deglazing the pan
Deglazing brings back some of the lost moisture and makes the onions even more delicious. Especially beer is excellent, and I almost always use it when I caramelize onions for burgers. 1-2 tablespoon (15-30ml) of liquid is enough.
Make ahead instructions
You can prepare them up to 2 days in advance and store them in an airtight container in the refrigerator. Let them cool down before putting them in the fridge. Before serving, reheat in the microwave for 1 minute or over medium-low heat for a few minutes until hot.
Once fully cooled, you can freeze them for up to 3 months. You can either freeze them in single servings or you can freeze them all in one freezer bag. To thaw, let sit on the counter for 30 minutes and then reheat.
Melt the butter and olive oil over medium-low heat. Add the onions and sprinkle with salt.
Cook uncovered over low heat for 45-60 minutes until golden or deep golden brown. Stir occasionally to avoid burning or sticking. You will need to stir more frequently towards the end of the process.
You will notice that the onions reduce a lot as they cook.
The picture below shows how they look when they are blonde.
Deglaze the pan in the last few minutes and cook the onions until golden or deep golden brown. Then serve.
What to serve them with
Caramelized Onions for Burgers
- 2 ½ tablespoon unsalted butter
- 1 tablespoon olive oil
- 2 large yellow onions
- ¼ teaspoon salt
- 2 tablespoon water, wine, or beer for deglazing the pan
- Melt the butter and olive oil over medium-low heat.
- Add the onions and sprinkle with salt. Cook uncovered over low heat for 45-60 minutes until golden or deep golden brown. Stir occasionally to avoid burning or sticking. You will need to stir more frequently towards the end of the process.
- In the last few minutes, deglaze the skillet by adding the liquid of your choice while scraping the bottom of the pan with a wooden spatula. Serve on burgers and enjoy.
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