Caramelized Onion Burgers

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Time was often not spent so efficiently in cooking school, and one morning our only task was to make French Onion Soup. We were separated into teams of two and lined up at our lengthy stove to watch onions caramelize and people cry from the sulfurous fumes while testing everyone’s patience for three hours.

The basis of any good French onion soup is, of course, the preparation of the onions. It’s a process that takes time to do properly and something that can’t particularly be rushed. Unfortunately, those unfamiliar with the process, especially with nothing else to occupy their time, and surrounded by others of similar disposition who have already jumped the gun and added the stock to soon, are faced with a daunting task to resist the temptation to do the same.

I was not one of those people since I already knew how long it took to caramelize onions (and also otherwise because I can listen to instructions), but that doesn’t mean I was spared the brunt of chef’s anger that morning for other people’s mistakes. No one is going to yell at you if you caramelize the onions wrong (that is, not caramelize them at all), but just know that as soon as you add liquid to something, you cannot caramelize it until that liquid evaporates.

Onions contain a lot of sugar, which is what makes them caramelize and enhances their flavorful sweetness, but they also contain a lot of water that takes a long time to remove. It’s truly amazing how much water is in fruits and vegetables that can be cooked down to nothing afterward. Caramelizing onions also increases their umami, or savoriness, which in turn makes them a perfect compliment to something you might want to taste meatier, like, say, meat. Therefore, I think they’re ideal and preferable in hamburgers, especially vegetarian/vegan ones that want a meaty oomph that pulses and rice just can’t quite muster on their own.

I like to put a bite of cheese inside of the burgers as a little surprise once you bite into it. Strong cheeses that pair well with beef and onions like blue cheeses, aged Cheddar (what I used tonight), Gruyere (like in French onion soup) are well suited to the task.


  • 2 tablespoons butter
  • 1 large Spanish onion, thinly sliced
  • 1 large red onion, thinly sliced
  • 1-star anise
  • 1/4 cup Balsamic vinegar
  • 2 tablespoons brown sugar
  • 1 pound lean ground beef
  • 1 egg
  • 1/3 cup fine bread crumbs
  • 3 ounces complimentary (not free) cheese(s), crumbled or cubed
  • salt and pepper


Melt the butter in a large skillet over medium heat until foamy, then add all of the onions, the star anise, and a generous pinch of salt and pepper. It will look like an enormous and unnecessary quantity, but it will cook down considerably, I swear. Cook negligently until the onion mass has reduced by more than half, then keep a watchful eye and stir occasionally as the onions begin to caramelize, as any burnt bits will transfer their bitter flavor to the whole batch. The whole process can take upward of an hour.
Once the onions have caramelized, add the balsamic vinegar and brown sugar. Reduce the vinegar until near entirely evaporated, then remove from the heat, discard the star anise (lest someone chip a tooth — bad surprise) and allow everything to cool to room temperature.

Once the onions have cooled, combine the caramelized onions, ground beef, egg, and bread crumbs. Season again with salt and pepper. With lightly wetted hands, roll small fist-sized (about four-ounce) patties in the palm of your hand and set aside. Press a piece of cheese (good surprise) in the center of each patty and form the meat around it to seal, then press lightly to flatten.

Heat a large grill pan or cast iron pan over medium heat until hot, then cook the burgers thoroughly, about 8-9 minutes per side, reducing the heat after the outside has seared to prevent scorching or otherwise finishing them in a 350-degree oven.

Serve on lightly toasted buns with your usual fixings, or some more unique pairings for the caramelized onion flavor, such as sliced figs, beets or cabbage. Reserve some of the caramelized onions for other purposes, if you wish, as there will definitely be enough to lend a hand here.

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