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Just 4 simple ingredients to make this rich caramelized onions and mushroom goodness. Perfect as a side dish, or toppings for your burgers and wraps! And honestly, it just makes any dish feels like a gourmet meal.

P.S. I’ve included a video that you can watch to make this recipe even simpler! Scroll down past the image below to watch! 😉

macro shot of caramelized onions and mushrooms with sprinkled salt and parsley

Watch the Recipe Video!

In this post you’ll learn:

Why You Will Love This Recipe

  • It’s so packed with flavor!
  • Adding it to any dish will make it a gourmet-like experience
  • It only requires 4 ingredients, 2 of which you should already have at home
  • Perfect for meal prep
  • With minimal oil, this recipe is way healthier than your usual caramelized mushrooms and onions
  • 100% plant-based, vegan, vegetarian, you name it

Ingredients

Just 4 simple ingredients, but so much flavor in this recipe!

  • Yellow onion: The star ingredient that gives this deep, rich, caramelized flavor. You can use other types of onions such as red onions and shallots so feel free to experiment!
  • Mushrooms: The second star ingredient! It gives an umami, meaty flavor to this dish, while still keeping it vegan🌱
  • Olive oil: The fat that adds even more flavor to this dish. Seriously, think of infused oil and how it’s so packed with flavor. The same thing is happening in our recipe! Feel free to sub this with vegan butter if that’s what you have at hand.
  • Salt: A bit of salt to amp up the flavor since salt is a natural flavor enhancer.
baby bella mushrooms, a yellow onion, olive oil, and salt in small white bowls

What Kind of Onions Can I Use?

Any kind of onion will work 😊

They could all be caramelized so I’d say just use whatever you have at home! The taste will vary slightly but you will still get that deep, rich, caramelized flavor. You can even use a combination of different varieties!

What Kind of Mushrooms Can I Use?

Use either baby bella mushrooms or white mushrooms. I find that baby bella mushrooms have a ‘meatier’ taste while white mushrooms have a slightly sweet note to them.

P.S. If you like mushrooms, I’ve written a thorough post on 35 Brown Vegetables, which also includes 6 different types of mushrooms!🍄

Step-by-step Instructions

Slice: Slice both the onion and the mushrooms.

For the onion, you want to prevent cutting through the root to prevent releasing the chemicals that make you cry. To do so, first cut it in half, right next to the root (but NOT through it). Then peel the skin off.

Next, with your knife facing the root, thinly slice the onion into 0.25 to 0.5 inch (0.6 to 1.3 cm) slices. Again, without cutting through the root. See the video below in the recipe card for a demonstration. (PS Thank you Gordon Ramsay for sharing this trick!)

For the mushrooms, slice them into 1cm (0.4 inches) thickness.

cutting a yellow onion into two, next to the root
Cut next to the root, but not through it
cut up yellow onion with the skin removed
Peel off the skin
removing the top of the onion
Cut off the top
pointing a knife to the root of the yellow onion, to avoid crying when cutting the onion
Point your knife to the root
cut up half of an onion, on a north-south direction
Slice the onion, without cutting through the root.
removing the root of an onion by cutting it away with a knife on a bamboo cutting board
Remove the root
slicing the other half of a yellow onion to make caramelized onion
Cut the other half onion with the knife facing the root/top (in a North-South direction)
slicing up the two ends of a yellow onion on a wooden cutting board
Slice the other half of the onion
cut up baby bella mushrooms on a bamboo cutting board
Slice your mushrooms

Add onions first: Heat the olive oil over medium heat. Then brown the onions first for about 5 minutes, until you get those fragrant sauteed onions. As always, aromatics should go first in the pan!

Add mushrooms: Now it’s time for the sliced mushrooms to go into the pan! Continue cooking for 20-25 minutes on low heat.

Keep an eye out: If it starts to look dry, splash 1 Tablespoon of water to deglaze. Only add 1 Tablespoon at a time because if you have too much liquid in your pan, they will steam instead of caramelize.

Salt: After 25 minutes, sprinkle the salt, stir, and turn off the heat to serve!

sauteed yellow onion on a black frying pan
sliced yellow onion and baby bella mushrooms after sauteeing for 10 minutes on a black frying pan
sliced baby bella mushrooms and yellow onion after sauteeing for about 30 minutes on a black frying pan
caramelized onions and mushrooms on a black frying pan, with a stirring spoon on the bottom right

Can You Caramelize Onions and Mushrooms Together?

Yes, you can! Mushrooms can be cooked for quite a long time without getting mushy. So you can add them early on when cooking, just like what I did in this recipe!

Toppings & Serving Suggestions

Want to amp up the flavor? I recommend adding some herbs or spices! Here are some tasty suggestions:

  • parsley
  • thyme
  • rosemary
  • paprika powder
  • garlic powder

What to Pair With Caramelized Onions?

I like to pair this caramelized mushrooms and onions recipe as fillings for my burgers, sandwiches (such as in this Hummus Bagel Sandwich recipe), and wraps. You can also serve this as a side dish with mashed potatoes, my Healthy Garlic Bread recipe, or Garlic Bread with Regular Sliced Bread recipe. I’ve also made pasta with caramelized onions and mushrooms and I can recommend that you try that combination too!

a fork holding caramelized onions and mushrooms with more caramelized onions in the background

Storage, Meal Prep, and Freezing Instructions

Storage: Store in an airtight container in the fridge for up to 5 days. Although kudos to you if you could keep this for 5 days because I always end up finishing them so quickly since it’s so delicious!

Meal prep: This recipe will last up to 5 days in the fridge so you can prepare ahead for the whole week. It’s the perfect recipe to batch-cook at the weekend when you have more time. You will be super excited for your next meal just thinking about how much flavor this recipe packs!

Freezing: Freeze in an air-tight container for up to 3 months. To heat up, just give them a quick stir fry in a pan. You can also microwave them when pressed for time.

How Do You Reheat Caramelized Onions?

Need to reheat your caramelized onions after storing them either in the fridge or the freezer?

You can quickly stir-fry the caramelized onions and mushroom again just before serving. Add splashes of olive oil or water to prevent them from sticking to the pan. Heat until everything is warm, for about 3-5 minutes depending on the portion size.

You can also simply microwave it for 30 seconds up to 2 minutes, depending on the portion size.

FAQs

Should you cover onions when caramelizing?

Nope, don’t do this. Covering the pan traps the liquid and it will steam instead of caramelizing the onions and mushrooms.

How often should you stir caramelized onions?

To put this simply, often enough so that it doesn’t get burned, but not too often so it can caramelize. I stir mine about every 5 minutes, but this will also depend on the exact type of pan that you’re using.

If you’re new to cooking, it’s better to stir it more frequently. This way, you might take more time until the onions are properly caramelized, but you would prevent burning which is irreversible!

Should onions be caramelized on medium or high heat?

I would actually advise caramelizing your onions on low heat instead. If the heat is bigger/stronger, you might risk burning.

But you might need to caramelize your onions on medium heat if you are cooking a big batch.

a close up shot of a fork holding a caramelized mushroom with more caramelized mushroom and onions in the background

Looking for more Easy Side Dish Recipe?

Check out some of these recipes!

Prefer something sweet instead? Check this out!

Print Recipe
5 from 2 votes

Caramelized Onions and Mushroom

Just 4 ingredients and 30 minutes to make this rich caramelized onions and mushroom goodness. Perfect as a side dish, or toppings for your burgers and wraps!
Prep Time5 minutes
Cook Time25 minutes
Total Time30 minutes
Course: Side Dish
Cuisine: American, French
Keyword: caramelized onions and mushroom
Servings: 4 servings
Calories: 190kcal

Ingredients

  • 1 large yellow onion sliced
  • 8 oz mushrooms baby bella or white, sliced (227 grams)
  • 2 teaspoons olive oil
  • ¼ teaspoon salt

Instructions

  • Slice: Cut the onion into halves, peel off the skin, then slice it thinly into 0.25 to 0.5 inches (0.6 to 1.3 cm). See video or post above for a demonstration.
    Thinly slice the mushrooms into 0.4 inch (1 cm) slices.
  • Add onions first: Heat a wide non-stick pan over medium heat and add the olive oil. Once the oil is hot (after about 30 seconds), add the onions. Stir occasionally for about 5 minutes. Be careful not to burn them by turning down the heat if necessary.
  • Add mushrooms: Once the onions become golden brown, add the sliced mushroom. Let it cook uncovered for another 20-25 minutes while stirring from time to time to prevent burning. Turn the heat to low if it starts to burn too quickly.
  • Splash (if necessary): If it starts to look dry, splash 1 Tablespoon of water to deglaze the pan. Repeat as necessary, but not too often (for me it took about 5 Tablespoons).
    In general, you want to be able to stir them without anything sticking to the pan, but you do not want liquid in your pan so that the onions can caramelize instead of being steamed.
  • Taste test: This dish is done when the onions turn dark brown and there is no crunch to them anymore. If they still taste a bit crunchy, cook a bit longer to let them fully caramelize.
  • Salt: Sprinkle the salt, mix, then turn the heat off immediately. Enjoy!

Notes

Storage, Meal Prep, and Freezing Notes:
  • Storage: Store in an airtight container in the fridge for up to 5 days. Although kudos to you if you could keep this for 5 days because I always end up finishing them so quickly since it’s so delicious!
  • Meal prep: It makes this recipe perfect to batch-cook at the weekend when you have more time. You will be super excited for your next meal just thinking about how much flavor this recipe packs!
  • Freezing: Freeze in an air-tight container for up to 3 months. To heat up, just give them a quick stir fry in a pan. You can also microwave them when pressed for time.