Caramelized Onions and Mushrooms only take a few ingredients to make, but taste so decadent. They’re the perfect topping or even side dish!
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Caramelized Onions and Mushrooms
While these take a little time to cook, it’s completely worth it for the earthy flavor that will be added to any dish. It’s such a versatile side dish or topping for just about anything.
The combination of butter, onions, and mushrooms will be something you’ll want to make weekly! Try adding it to your steak or burger the next time you grill out.
These are the perfect side for a juicy grilled flank steak. They’re also delicious on this rustic pizza with goat cheese and balsamic reduction, where they pair so well with the creamy goat cheese and bright balsamic.
If you already have a batch made, use them in place of the chipotle onion jam on these burgers with grilled peaches. Or spoon a little over this baked chicken caprese for some extra earthy flavor.
Note from the Author
2026 Update: When I first shared this recipe back in 2020, it was a simple version with just the basics. I’ve since updated it with more tips and step-by-step details so you’ll have everything you need to make the most flavorful, golden caramelized onions and mushrooms at home.
Step by Step Instructions
Check out the recipe card below for more in-depth instructions for how to caramelize onions and mushrooms:
- Slice: Slice your onion into about ¼-inch half moons and wipe the mushrooms clean (or grab pre-sliced mushrooms to save a step). Don’t go paper-thin on the onions. Thin slices burn before they ever get sweet.
- Melt: Melt the butter in a large skillet over medium-low heat. Cast iron is my favorite here, but any wide, heavy pan works.
- Cook low and slow: Add the sliced mushrooms, sliced onions, and pepper and stir to coat. The mushrooms release a lot of liquid at first. Let it cook off, stirring every few minutes and scraping the bottom of the pan. Don’t rush this part and crank it up to medium-high heat, because this is where the flavor magic happens.
- Deglaze and finish: If browned bits start sticking, add a splash of water and scrape them up. That’s pure flavor. Season with salt at the end of cooking, then serve warm.
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Recipe Testing Notes and Tips
As a recipe developer with a degree in food science, I create approachable recipes you can trust. Here are a few takeaways:
- Reach for sweet onions if you can: Vidalia or other sweet onions caramelize beautifully thanks to their natural sugars. Yellow onions work great too, but sweet onions get you to that jammy stage a little faster.
- Give them room: A large skillet matters more than you’d think to keep them in a single layer. When cooking mushrooms in a crowded pan, they steam in their own liquid instead of browning, and you lose that meaty texture.
- Salt at the end: Salt pulls moisture out of mushrooms, so adding it early leaves you with a soggy pan. Stir it in at the end of cooking for the best browning.
- Mix up your mushrooms: Baby bellas (cremini) are my go-to, but white mushrooms or oyster mushrooms are great too. Just keep all the slices about the same thickness so they cook evenly.
- Butter or oil: If your butter starts browning too fast, swap a tablespoon of it for a little oil like olive oil. The oil can take more heat, and you still get the buttery flavor.
- Let’s nerd out: Two kinds of browning are happening in one pan. The onions are caramelizing, meaning their natural sugars are breaking down into those sweet, toasty notes. The mushrooms brown through the Maillard reaction, which can’t really start until their water cooks off. That’s why patience (and an uncovered pan) is everything here.
Tip
If you love that deep, golden color on your caramelized onions and mushrooms, then a cast iron skillet is a must-have!
Variations for your sauteed mushrooms and onions
- Balsamic glazed: Stir in a splash of balsamic vinegar at the end of cooking for a tangy-sweet finish that’s incredible on steak.
- Steakhouse style: Add a dash of Worcestershire sauce and a pinch of brown sugar for a rich, savory burger topping.
- Garlic and white wine: Toss in minced garlic for the last 2 minutes, then deglaze with white wine instead of water.
- Dairy-free: Swap the butter for olive oil or a plant-based butter. You’ll lose a little richness but none of the flavor.
- Herby: Add a few sprigs of fresh thyme while they cook for an earthy, woodsy twist.
Recipe FAQs
Just about anything you can think of! This caramelized onions and mushrooms recipe goes with steak, burgers, pizza, chicken, grain bowls, pasta, or piled high on sandwiches. Any dish you’d love to add a savory pop to is fair game.
Yes! In an airtight container, these sauteed mushrooms and onions will last 3 to 5 days in the refrigerator. I usually go through them much faster, but they’re great to make ahead if you know you’ll need them for a dish later in the week.
You don’t want to cover the pan while they are caramelizing as it will trap in the liquid that you’re looking to cook out of the mushrooms especially. If there is too much liquid, it won’t get the browned edges that you’re looking for.
It takes longer than you’d think! I’d allot around 40 – 60 minutes to caramelize the onions and mushrooms. You want to do it over a low heat so that it doesn’t burn while also stirring occasionally to ensure that the cooking process is even.
You’ll want to use a pan with a large surface area so that it isn’t crowded. More space allows for the caramelization process to happen more evenly and for the moisture to escape.
Yellow onions are easy to caramelize because of their natural sugars. Be sure not to cut them too thin, though, or they’re more likely to burn. You can also caramelize red onions for a different flavor, but they do better cooked on their own.
Baby bella mushrooms are my favorite to use for their deep flavor to start. You can buy them pre sliced, but if you wash them you’ll want to make sure they are sufficiently dry before add the mushrooms to the pan.
Warm them in a skillet over medium heat with a splash of water, or pop them in the microwave for 30 to 60 seconds, stirring halfway through.
You can! Freeze them in portions for up to 3 months. The mushrooms get a little softer once thawed, so they work best stirred into pasta, sauces, or soups, not as a topping.
Caramelized Onions and Mushrooms
Caramelized Onions and Mushrooms only take a few ingredients to make, but taste so decadent and make a great side dish or topping.
Ingredients
- 3 tablespoons butter
- 8 ounces sliced mushrooms
- 1 large onion, sliced
- ¼ teaspoon pepper
Instructions
- In a large skillet, melt butter over medium-low heat.
- Add in sliced mushrooms, sliced onions, and pepper and stir to coat.
- Continue to let simmer uncovered for 30 minutes, stirring every few minutes to ensure that the bottom doesn’t burn.
- Remove from heat and enjoy warm or cool to room temperature then refrigerate. Enjoy!
Notes
- Storage: Cool the onions and mushrooms completely, then store them in an airtight container in the fridge for 3 to 5 days.
- Freezing: Freeze in small portions for up to 3 months. The mushrooms soften a bit after thawing, so frozen batches are best stirred into pasta, sauces, or soups.
- Reheating: Warm them in a skillet over medium heat with a splash of water, or microwave for 30 to 60 seconds, stirring halfway through.
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Nutrition Information:
Yield: 4 Serving Size: 1Amount Per Serving: Calories: 107Total Fat: 9gSaturated Fat: 6gTrans Fat: 0gUnsaturated Fat: 3gCholesterol: 23mgSodium: 71mgCarbohydrates: 6gNet Carbohydrates: 0gFiber: 2gSugar: 3gSugar Alcohols: 0gProtein: 2g
