Good things come to those who wait. Perfectly caramelized onions and mushrooms are a game-changer for any meal, whether you pile them onto burgers, stir them into pasta, or use them to top sandwiches and crusty bread.
Ingredients You’ll Need
Caramelizing mushrooms and onions draw out the deep, rich flavors of the veggies to add a savory sweetness to any dish. Here’s what you need to make them:
- Olive Oil & Butter: A mix of extra-virgin olive oil and butter is the best way to caramelize the onions and mushrooms. The butter adds flavor, while the oil prevents the ingredients from sticking or burning.
- Onions: Yellow onions are the best for caramelizing, but use white onions, sweet onions, and even shallots.
- Mushrooms: Feel free to use your preferred mushrooms—cremini mushrooms, baby Bella mushrooms, and button mushrooms are my favorite!
- Salt: Use kosher salt to bring out the flavor of the veggies. It coats the food without being as salty as table salt. You can also add black pepper, garlic powder, or dried herbs to suit your taste.
Additions and Substitutions
- Include aromatics. Fresh garlic pairs perfectly with onions and mushrooms. Add the minced garlic at the end once the veggies are caramelized to prevent the garlic from burning.
- Keep it fresh. Incorporate herbs like thyme, rosemary, or parsley.
- Deglaze the pan. The mushrooms release moisture to infuse the veggies with flavor, but add a splash of balsamic vinegar, soy sauce, Worcestershire sauce, or red wine to deglaze the pan for additional flavor.
Tools Used to Make This Recipe
The best pan for making caramelized onions and mushrooms is a large, heavy-bottomed skillet or sauté pan. Cast-iron or stainless steel works best for even heat distribution to achieve a deep caramelization. You’ll want to use a pan with a large surface area. More space allows for better caramelization and moisture evaporation.
How to Make Caramelized Onions and Mushrooms
The full recipe with measurements is in the recipe card below.
Step 1: Peel the onions and thinly slice them, about ⅛-inch thick. Wipe the mushrooms with a cloth or paper towel for the best results. Then, remove the bottom part of the stem and cut the mushrooms into ¼- inch thick slices.
Step 2: Warm the olive oil in a preheated stainless steel skillet or cast-iron skillet over medium-low heat.
Step 3: Then, add butter and onions. Saute for 15-20 minutes until the edges start to turn brown.
Step 4: Stir in the mushrooms and continue cooking over medium-low heat for 5-10 minutes without stirring.
Step 5: Once the onions and mushrooms are golden brown, stir in the kosher salt and cook for 5 minutes.
Expert Tips
- Keep it low and slow. The key to perfectly caramelized onions and mushrooms is patience. Cook the onions and mushrooms on medium-low heat, allowing the natural sugars to break down without burning, resulting in a rich, golden-brown color.
- Use a large pan. Use a large skillet so the onions and mushrooms have space to cook and release and reabsorb the moisture.
- Don’t overcrowd the pan. Crowding the pan traps moisture, causing the ingredients to steam rather than caramelize.
- Be patient. Caramelization takes time, around 25-30 minutes. Stir occasionally but not too often so they have time to brown. Once you add the mushrooms, they release liquid. Don’t get hasty and increase the heat – once the liquid evaporates, the mushrooms will start sizzling again.
- Season at the end. Add salt once the mushrooms have browned and the onions are soft and golden.
How Long to Cook Onions and Mushrooms?
| Soften | 3-5 Minutes | |
| Tenderize | 5-10 Minutes | |
| Caramelize | 25-30 Minutes | They need to cook long enough for the liquid to release from the onions and mushrooms and evaporate. |
If you enjoy the flavorful side, pair them with one of these dinner recipes!
Serving Suggestions
Caramelized onions and mushrooms are a versatile side dish or topping. Use them to finish tasty sheet pan burgers or add them to breakfast recipes—scrambled eggs, omelets, and quiches.
Add the veggies to soup, stew, pasta, and stir-fried recipes, or use them to top a slice of Dutch oven sourdough bread with whipped ricotta tip for a savory sweet treat.
For a few more recipes to pair them with, try air fryer turkey burgers, grilled bison steaks, and risotto allo zafferano.
What to do with the Leftovers
- Refrigerate: Store leftover mushrooms and onions in an airtight container for 5-7 days.
- Freeze: It’s possible to freeze caramelized mushrooms and onions. However, it’s important to note that they will change consistency in the freezer since the vegetables naturally contain water. Let the mushrooms and onions cool and transfer them to an ice tray. Once frozen, you can place the cubes in a freezer-safe container or bag. They will freeze for three months.
- Reheat: Add them directly to the pan and cook over medium heat or warm individual serving in the microwave.
- Repurpose: Use the leftover caramelized onions and mushrooms to make mushroom stew or mushroom fried rice, or incorporate them into meals like easy beef stroganoff or vegan hamburger helper.
Frequently Asked Questions
Do caramelized onions need salt?
Salt isn’t necessary, but it does help draw the moisture from the onions and mushrooms so they can sear and caramelize. Skip the salt and extend the cooking time to achieve a similar result.
Should I cook onions or mushrooms first?
I prefer to cook the onions first, let me explain. Onions take longer to caramelize, so adding them first makes sense.
When you add the mushrooms to the hot pan, they will release moisture. And while you risk the onions becoming soggy, the extra moisture helps to deglaze the pan to infuse the mushrooms and onions with rich, umami flavor (no need for red wine vinegar, soy sauce, or Worcestershire unless you want it).
Continue cooking, and all the extra moisture will evaporate, leaving you with a flavorful side dish or topping.
Should I cover the pan?
There is no need to cover the pan with a lid. Doing so will actually work against you because it traps the liquid inside the pan, causing the onions and mushrooms to become soggy instead of caramelized.
More Vegetable Recipes:
Caramelized Onions and Mushrooms
- 1 tablespoon olive oil
- 2 tablespoons butter
- 1 large yellow onion, ⅛-inch slices
- 1 package (8 ounces) bella mushrooms, ¼-inch slices
- ½ teaspoon kosher salt
- Peel the onions and thinly slice them, about ⅛-inch thick. Wipe the mushrooms with a cloth or paper towel for the best results. Then, remove the bottom part of the stem and cut the mushrooms into ¼- inch thick slices.
- Warm the olive oil in a preheated stainless steel skillet or cast-iron skillet over medium-low heat. Then, add butter and onions. Saute for 15-20 minutes until the edges start to turn brown.
- Stir in the mushrooms and continue cooking over medium-low heat for 5-10 minutes without stirring.
- Once the onions and mushrooms are golden brown, stir in the kosher salt and cook for 5 minutes.
- Keep it low and slow. The key to perfectly caramelized onions and mushrooms is patience. Cook the onions and mushrooms on medium-low heat, allowing the natural sugars to break down without burning, resulting in a rich, golden-brown color.
- Use a large pan. Use a large skillet so the onions and mushrooms have space to cook and release and reabsorb the moisture.
- Don’t overcrowd the pan. Crowding the pan traps moisture, causing the ingredients to steam rather than caramelize.
- Be patient. Caramelization takes time, around 25-30 minutes. Stir occasionally but not too often so they have time to brown. Once you add the mushrooms, they release liquid. Don’t get hasty and increase the heat – once the liquid evaporates, the mushrooms will start sizzling again.
- Season at the end. Add salt once the mushrooms have browned and the onions are soft and golden.
- The nutritional information shown is an estimate provided by an online nutrition calculator. It should not be considered a substitute for professional advice.