Steps To Perfect Caramelized Onions And Mushrooms

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Caramelized onions and mushrooms are the perfect topper for chicken or steak. You can even make them into a delicious sauce to eat alone.

Caramelized onions and mushrooms

One thing I love to top my steaks with are caramelized onions and mushrooms. Sautéed mushrooms are amazing alone but caramelized onions bring in their natural flavors. Along with the natural sweetness that comes with letting them cook on low heat for an extended amount of time.

How To Caramelize Onions And Mushrooms

Ingredients Needed

  • Yellow Onion
  • Baby Bella, White Mushrooms or Shiitake Mushrooms*
  • Thyme
  • Oil
  • Butter
  • Salt & Black Pepper

Helpful Recipe Tips

  • Avoid chopping mushrooms or onions up too finely. What will happen is they will get mushy and you want to still have a bite to the vegetables. Make sure they are at least quarter of an inch thick.
  • Keep moisture in the pan. Throughout cooking the pan can start to look dry. When this happens don’t add the butter in, add in a bit more olive oil.
  • Use a pan that allows sticking to speed up the process. A non-stick pan isn’t the best pan to use for caramelized onions and mushrooms.

Cooking The Recipe

  1. First, in a frying pan on medium high heat add a little oil then only the mushrooms. Cook them about 3-4 minutes and allow them to “sweat” a little. You will notice the water releasing from the mushrooms.
  2. Next, toss in a sliced onion. Add a little more oil, about one tablespoon.
  3. Continue to cook on medium high and stirring contantly.
  4. Once you start notice the onions and mushrooms sticking to the pan lower the heat to medium. When this happens the majority of the water has evaporated and now the caramelization will start. This will take 5-10 minutes but now you have to pay close attention to the pan.
  5. Stir often to avoid burning. To speed the process up is to allow the mushrooms and onions to stick then stir them. This way they won’t burn.
  6. When everything has a beautiful brown color and are withered lower the heat to medium low. Toss in a tablespoon of butter and a few stems of thyme. The butter will not only deglaze the pan a little but will also add more flavor to the caramelized onions and mushrooms.
  7. Serve.
step by step instructions 3

How To Store Caramelized Onions And Mushrooms

Storing is the best part about this onions and mushrooms recipe. Simply place them in a sealed container in the refrigerator for 3-4 days. The easiest part is reheating.

To reheat this caramelized onions and mushrooms recipe turn a frying pan on medium heat with a little oil. Toss in the cold recipe and stir until reheated. They will taste just like they did the day you made them.

Caramelized onions and mushrooms

Frequently Asked Questions (FAQs)

How To Slice An Onion

Why do onions make you cry? Well, when you look at an onion there are 2 sides to each. One side is the top where you can peel the outside back and the other end is the bulb. The bulb is what makes you cry when peeling an onion. When you slice into it and each time you slice it a chemical is released into the air.

I slice my onions down the middle just once. This exposes the bulb and I know how far to cut back. Now, because you cut it you will release some of that chemical but it won’t be bad. What you can do is cut the area where the bulb is off and quickly put it into the trash.

Now that the onion is split in half add the flat side down and cut long slices towards the end. See video for final cut example.

What kind of onions and mushrooms to use?

My favorite mushrooms are baby bella and shiitake for this recipe. Yellow or sweet onions are always the best and only onions you should use to caramelize. They have the most sugar out of all the onions.

How long does it take to caramelize?

Some people say an hour but honestly it shouldn’t take more than 20 minutes for this recipe. The skill comes in a heat being high enough and using the proper pan. Allow the onions and mushrooms to stick a little then stir them. If your heat is too high they will burn but if too low they won’t caramelize correctly.

Do you use oil or butter to caramelize onions and mushrooms?

Always use oil first and finish with butter. Oil is designed for higher heat cooking and butter is not. You can use ghee which is clarified butter but not regular butter. Use butter at the very end at a lower heat for maximum flavor.

Should I add sugar?

No you don’t need to add sugar to this caramelized onions and mushrooms recipe. The natural sugars from each combined with the proteins with caramelize themselves once the water has evaporated from the vegetables. It doesn’t speed up the process the browning you see is the sugar and it will be quite sweet.

How to make caramelized onions and mushrooms sauce?

At the last step, instead of adding butter don’t lower the heat. Add in 1/2 cup of marsala wine and allow it to cook off the alcohol. Reduce the heat after adding the wine. Then, add in a tablespoon of creme fraiche then stir until the sauce thickens. Taste for salt then serve.

Caramelized onions and mushrooms with marsala sauce

Do I cover the pan?

Never! The water will pool in the frying pan and you will have boiling onions and mushrooms instead of caramelized.

What to serve with caramelized onions and mushrooms

  • Pizza
  • Burgers
  • Chicken Breast
  • Steak
  • Flatbread
  • Quiche
  • Flaky, pastry bites
Caramelized onions and mushrooms

Caramelized onions and mushrooms

Caramelized onions and mushrooms are the perfect side dish or topper. Mushrooms and onions are both healthy vegetables and when you add butter into the mix they become one of the tastiest combinations ever. Mix in a little fresh herbs in this great side dish option.
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Prep Time 10 minutes
Cook Time 15 minutes
0 minutes
Total Time 25 minutes
Course Side Dish
Cuisine American
Servings 3 servings


  • 8 ounces mushrooms
  • 1 yellow onion
  • 3 stems thyme (sub with 1 tsp dried thyme)
  • 1 tablespoon butter
  • oil for cooking

Marsala Sauce

  • 1/2 cup marsala wine
  • 1 tablespoon creme fraiche


  • Slice onions and mushrooms and remove the leaves from thyme stems.
  • In a frying pan on medium high heat add about 1 TB oil and then toss in mushrooms. Cook and stir the mushrooms for about 3 minutes to allow them to release some water.
  • Then, add in sliced onions. Continue mixing around for about 3-4 minutes. Once the onions and mushrooms start to stick to the bottom of the pan lower the heat to medium.
  • If the pan gets too dry add a little oil when needed. Continue to stir, let it stick for a second then stir again. This speeds the process up. If you let the mushrooms or onions stick for too long they will burn. You will have to stay at the stove while cooking this recipe.
  • When the majority is browned and withered lower the heat and to medium low and toss in thyme. Mix it around then toss in butter. Mix well then salt and pepper to taste.
  • Serve.

Marsala Sauce

  • Starting from step 5 above.
  • Do not lower the heat or add butter. Instead pour in marsala wine. Allow the alcohol to cook off (where there isn't a strong smell coming from the pan) then lower the heat to medium low.
  • Toss in the thyme and creme fraiche. Mix everything around until the sauce forms then salt and pepper to taste.


Keyword Caramelized onions and mushrooms
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