If you enjoy caramelized onions and mushrooms with your steak, or as a burger topping, or just to eat, you are going to LOVE this no-fuss air fryer recipe. This method replaces standing over the stove sautéing mushrooms and onions and is pretty much hands-off except for tossing things around midway through the cooking time.
What I love most about this recipe, besides being super easy, of course, is the texture of the onions and mushrooms when they are done. They aren't crispy, but the texture is slightly firmer than when sautéed and I love that! The buttery flavor and caramelization with the slightly firmer texture are simple magic and the perfect side dish.
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If you are looking for a breaded mushroom recipe made in the air fryer, be sure to check out my recipe for easy air fryer mushrooms. or for stuffed mushrooms, check out this recipe for air fryer stuffed mushrooms.
If it's crunchy onion rings you are after, try this recipe, best air fryer onion rings. Or, maybe you want a crunchy onion topping for a casserole. If so, make some onion straws and I show you how in this recipe, Green Bean Casserole with homemade onion straws.
This recipe results in a flavorful bowl of mixed onions and mushrooms that will closely remind you of sautéed mushrooms and onions like you would make in a frying pan on the stove with some olive oil and butter.
Serve these along with a sous vide sirloin steak and you will think you are dining in an upscale steak house. Don't take my word for it, though; give this classic combination a try today!
Ingredients & Substitutions
Onion
I used a Vidalia or sweet onion in this recipe because I've always loved the extra sweetness, but you can use any variety of onions that you love.
I will say that green onions are not going to work in this recipe unless you only used the white part of the onion and you would need a whole lot of green onions, so skip those. Other than that you can use yellow onion, red onion, white onion, and even shallots would work.
If you don't like onions but love mushrooms, skip the onions and double up on the mushrooms for wonderful air fryer "sautéed" mushrooms
You could also use other vegetables in place of the onions like, sliced bell peppers or even squash slices. Since squash contains more water and cooks faster, I would add them halfway through the cooking time.
Mushrooms
Cremini mushrooms or also known as baby bellas are my absolute favorite mushroom to use in this recipe. They are small like white button mushrooms, but have the flavor of portobello mushrooms which is a little more earthy flavor.
You can use sliced portobello mushrooms in this recipe if you can't find the baby bellas. The size of the mushroom isn't going to matter because you can either slice them or quarter them so they all cook at the same time.
You can also use different types of mushrooms, especially if you don't like onions and are just making air fryer buttery mushrooms. A combination of baby portobello, white mushrooms, and shitake mushrooms would be incredible.
If you don't like mushrooms, but love onions, skip the mushrooms and triple up on the onions. Since the mushrooms are bulkier and don't cook down as much as the onions do, I recommend using a total of 3 medium size onions if you are skipping the mushrooms.
You could also substitute the mushrooms with sliced bell peppers of any color if you wanted an air fryer onion and pepper side dish.
Seasonings
Basic seasonings like salt and black pepper are all you really need in this recipe, but you can also use your seasoning of choice.
I like to add a little dried thyme leaves because I love the flavor. I don't recommend using thyme powder because it is too concentrated and can overpower the vegetables.
Garlic powder and onion powder would also be nice additions, just make sure not to use too much.
If you were serving the mushrooms and onions as a pizza topping, add a pinch of Italian seasoning. If you want to serve them with a cheesesteak and want a bit of spice, add a pinch or two of red pepper flakes. I consider a pinch to be about ¹⁄₁₆ of a teaspoon, so 2 pinches would be ⅛ of a teaspoon. 4 pinches would be ¼ teaspoon.
The idea with the dry seasonings is to bring out the flavors of the mushrooms and onions, not cover them up. A little spice goes a long way, so start off with just a pinch or two of seasoning and, if you need to add more after they finish cooking, you absolutely can.
I found this out the hard way when I used too much salt in the beginning and the dish was super salty at the end and I didn't have any way to fix it. Also, keep in mind what other liquid types of seasonings you are using and take into account their salt content.
I also like to add a touch of balsamic vinegar when making air fryer mushrooms and onions. This is completely optional, but I like the touch of acid and sweetness that comes from the balsamic vinegar.
You could also use a bit of red or white vinegar, soy sauce, or Worcestershire sauce, if you prefer. It's also perfectly fine to skip the liquid seasoning.
Fat
In my opinion, it is necessary to add some sort of fat to "sauté" the onions and mushrooms in the air fryer. I realize that many people purchase air fryers to eliminate or reduce fat, so you can skip it, but if you do make sure to add some kind of liquid seasoning like balsamic vinegar or your onions and mushrooms will become too dry in the air fryer.
I like to use a combination of olive oil and butter. The olive oil coats the vegetables as they are air frying and the butter goes on at the end to create a luscious sauce that coats the veggies perfectly.
You can use any kind of oil that you like and the butter can be salted or unsalted. You can also skip the butter if you want to keep the side dish vegan.
Garnishes
Although completely optional, a little sprinkle of either dry or fresh parsley really brings a boost of color to the dish without altering the flavor.
If you skipped the dried thyme leaves and have fresh thyme, use it as a garnish and it will be amazing. A small amount of fresh rosemary is also a great option. Just don't use too much, because rosemary is a very powerful flavor.
How to Make Air Fryer Mushrooms & Onions
Prep or Mise En Place
Cut the onion in half from root end to stem end and remove the paper from the onion. Sometimes you will also need to remove the first onion layer. Lay the flat side of the onion on your cutting board and slice it into about ½" slices.
Cleaning Mushrooms can be done several ways. I use a damp paper towel and gently wipe off any dirt. You can also give them a quick rinse under cool water and pat them dry. You don't want the mushrooms to be wet when you add them to the air fryer or they will create too much steam and the vegetables won't have the same texture.
Once the mushrooms are clean, trim the stem off of the whole mushrooms and, if you are using white button or cremini (baby bella) mushrooms, I like to quarter them. You can also slice them into ½" slices, if you prefer.
If you are using large portobello mushrooms, I would quarter them and slice them so they are in bite-size pieces.
Place the sliced onions and cut mushrooms into the bottom of the air fryer basket. You do not need a rack for this, keep them on the bottom of the basket.
You do not need to preheat the air fryer for this recipe, so add the onions and mushrooms direct to the air fryer inner pot or basket before seasoning to avoid dirtying a bowl.
I have also tested this recipe in the Ninja Foodi Pressure Cooker & Air Crisper, the Ninja Foodi Indoor Grill, and the Ninja Speedi and you do not need to make any changes if using one of these appliances.
Seasonings
Add the olive oil, salt, and pepper to the mushrooms and onions and toss them around to coat.
If you want to add the dry thyme leaves and balsamic vinegar, do that now and toss to coat.
Air Frying Mushrooms & Onions
Set the temperature on your air fryer to 400℉/200℃ and the time for 30 minutes. It does not take 30 minutes for the mushrooms and onions to cook, but I like to have extra time on the clock. It usually takes anywhere from 17-23 minutes to cook the onions and mushrooms and that depends on the air fryer you are using and the texture you want them to be.
Toss the mushrooms and onions around after 10 minutes of cooking and resume air frying.
After about 17 minutes of air frying, use tongs or a fork to remove an onion slice and a piece of mushroom. Taste them to see if they are cooked enough for you. If they are, proceed to the final touches.
If you want them softer, continue air frying and check the texture after another 3-5 minutes.
Final Touches
When the mushrooms and onions are the texture you like, add in the butter and toss the mixture around. Close the air fryer and keep it off. Let it sit for 3-5 minutes to give the butter time to melt.
Toss it all around and place the air fryer mushrooms and onions into a serving bowl.
Top with dry or fresh parsley if desired.
Serve & Enjoy!
What to Serve with Air Fryer Mushrooms & Onions
Mushrooms and Onions go with just about anything and can be used in so many different ways. They can be served in a bowl as a side dish or top them with panko and cheese and bake for a casserole type of side dish.
You can use them as toppings for so many things like pizza and subs or use them as an ingredient in things like omelets, quiches, and casseroles.
Here are some of my favorite ways to use Air Fryer Mushrooms and Onions
- Steak & Cheese Sub topping
- Pizza Topping
- Top a cooked chicken breast with the onions and mushrooms and a little shredded Swiss and bake, broil, or air fry until the cheese melts.
- Top a steak with the onions and mushrooms and pour over a little béarnaise sauce or your favorite type of steak sauce.
- Use as a burger topping
- Use any leftovers in an omelet, scrambled eggs, or quiche.
- Use the mushrooms and onions in fajitas or quesadillas
These are only a few uses, there are countless ways to use and serve these delicious air fryer mushrooms and onions. So, get creative and be sure to leave a comment with your favorite way to serve them!
Frequently Asked Questions
Yes, you can. However, they are going to have a better texture freshly made. I would recommend using the frozen and thawed mushrooms and onions in casserole dishes or as an ingredient in soup.
To freeze the leftovers, make sure they are cold, then package them in a freezer container or vacuumed sealed bag and make sure to include the juices to help prevent freezer burn.
You can make as much or as little of the mushrooms and onions as you like by simply increasing or decreasing the ingredients. Depending on your air fryer, you may need to cook them in batches. If you double the recipe, plan on cooking longer and toss them every 8 minutes so they all cook evenly.
Yes, of course! Just adjust the cooking time according to the type of vegetable you use. For example, you can use a combination of potatoes and onions, but you would want to add the chunks of potatoes first and cook about 10 minutes and then add in the onions and cook another 15 minutes or so.
If you wanted a combination of onions, mushrooms, and squash, add the squash after the first 10 minutes of cooking because it has a higher water content and will cook much faster.
More Delicious Air Fryer Recipes
Until I purchased the Ninja Foodi Pressure Cooker & Air Crisper, I had never owned an air fryer. Now, I have many different styles and love them all! Air fryers are perfect for making so many things, here are some of my favorites that I hope you love as much as I do.
- Ninja Foodi Chicken Tenders (Air Fryer Chicken Strips)30 Minutes
- Air Fryer Meatloaf50 Minutes
- Air Fryer Chicken Cordon Bleu45 Minutes
- Air Fryer Coconut Shrimp in the Ninja Foodi (or any Air Fryer)16 Minutes
- Air Fryer Crab Rangoon30 Minutes
- Air Fried Cauliflower with General Tso's Sauce30 Minutes
- Air Fryer Croutons25 Minutes
- Ninja Foodi Sweet Potato Fries20 Minutes
Air Fryer Mushrooms & Onions
Equipment
- Air Fryer
Ingredients
- 1 medium sweet onion or any onion
- 8 ounces mushrooms
- 2 Tablespoons olive oil
- ¼ teaspoon fine grind sea salt
- ⅛-¼ teaspoon black pepper
- ⅛-¼ teaspoon dry thyme leaves optional
- 1 Tablespoon basalmic vinegar optional
- 2 Tablespoons butter salted or unsalted
- dried or fresh parsley optional
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Instructions
- Slice the onion into ½" strips. Quarter the cremini mushrooms. Make sure the mushrooms are not wet when adding them to the air fryer or too much steam will be produced and the texture will be different.1 medium sweet onion, 8 ounces mushrooms
- Add the prepared onions and mushrooms to the inner cooking surface of your air fryer. So, if you are using the Ninja Foodi Pressure Cooker & Air Crisper, this would be the inner pot. On basket style air fryers, this would be the basket without a rack.
- Add the olive oil, salt, and black pepper. Use tongs to toss the vegetables around so they are evenly coated.2 Tablespoons olive oil, ¼ teaspoon fine grind sea salt, ⅛-¼ teaspoon black pepper
- If you want to add the optional seasonings, do that now and toss to coat.⅛-¼ teaspoon dry thyme leaves, 1 Tablespoon basalmic vinegar
- Close the air fryer and select the air fry function, set the temperature to 400℉/200℃ and the time for 30 minutes. It does not take 30 minutes to finish cooking, but I like to have the extra time on the clock. Hit start.
- After 8-10 minutes, open the air fryer and toss the onions and mushrooms around. You will see more liquid has collected in the bottom and you want to coat the vegetables with it. Continue air frying another 7-10 minutes.
- After 17 minutes, open the air fryer and taste one of the onion slices and a mushroom piece. If they are the correct texture for you and seasoned well, then proceed to the final touches. If you want them softer, continue air frying for another 5-10 minutes or until they are the texture you like. Add salt and pepper if needed, but if you are going to add salted butter at the end, then be careful with the salt.
- Once the mushrooms and onions are the texture you like, add the butter and close the lid or drawere of the air fryer. With the air fryer turned off, leave the mushrooms and onions inside so the butter melts from the residual heat for 3-5 minutes.2 Tablespoons butter
- Toss the mushrooms and onions around with tongs and transfer to a serving bowl. Top with dry or fresh parsley if desired. if you didn't use dry thyme leaves, you can garnish with fresh thyme leaves instead of parsley. Serve & Enjoy!dried or fresh parsley
Notes
Nutrition
About the Recipe Author, Louise Long
Louise is a full-time recipe creator and food blogger @ The Salted Pepper. She has over 30 years of experience with cooking and recipe development. She owned a restaurant for several years and was a full-time RN until retiring to blog full-time.
She published her first cookbook in the Fall of 2018 and is very interested in writing several more.
Louise is also the creator of an online Ninja Foodi Pressure Cooking Course with over 100 instructional step-by-step videos. People absolutely rave about the course and all the value they have received from it.
Louise has several very active Facebook groups that help people with the basics of cooking and learning more about the appliances they love.
Ninja Foodi Pressure Cooker & Air Crisper 101
Ninja Woodfire Outdoor Grill & Smoker
Louise is also a YouTube creator and you can find most of her recipes in video format on The Salted Pepper YouTube channel.
She is very responsive to messages and eager to help in any way she can. Get more Information about Louise & contact information
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JimmyB
I used your recipe for guidance last night and the outcome was delicious! I only used baby bella mushrooms, no onion. I was fixing these in preparation for pizza topping so did not bother with the extra seasoning. I just used olive oil, salt and pepper. I did them in an air fryer at 360° for 10 minutes and they were perfect. Thanks for teaching such a great way to prepare them.
Louise
I'm so happy to hear that! I hope your pizza was delicious!