A rich mushroom side dish perfect for serving with burgers, steaks, pasta and more, a good pan of caramelized onions and mushrooms is something everyone should know how to make. With only a few simple ingredients the technique is extremely important here. Today I'll show you how to make it like a pro.
You might assume the dish starts by cooking mushrooms and onions together, and you wouldn't be alone. But, for the best result, it's actually much better to caramelize the onions separately, then brown the mushrooms and combine the two later.
The mushrooms are flexible. I'm using a hen of the woods mushrooms / maitake, but you can use just about any mushroom you want. The onions and how they're treated are different, and I'm extremely picky about how they're cut and cooked.
The most important part of this recipe is the onions. While you could technically make it with many kinds of onions, sweet onions like a vidalia, candy onion or Walla-Walla are my favorite.
Red onions are my least favorite, but shallots are good. Even more important than the variety is the way the onions are cut, which is what we'll cover first.
How to Properly Cut an Onion
Despite what some may say, there is a right and wrong way to cut onions for general cooking. Of all things food, this is by far my biggest pet peeve. I know it sounds unappetizing, but when cut the "long" way, onions are too chewy and have an unpleasant texture I compare to tapeworms. See the infographic below.
But, even before you slice the onions a great tip to know is that many onions, especially those that have been stored for a time need to have their outer skin, as well as the first layer of flesh discarded as it's typically tough. Just one tough onion layer can ruin a dish.
To slice the onion into the thin strips you'll caramelized cut the top and bottom from the onions, remove the skin and tough outer layer. Next, place the onions cut side down and cut them perpendicular to the equator as shown below.
I like them short, about an inch long, but it's ok to have them a littler longer.
How to Make Caramelized Onions and Mushrooms
After the onions are sliced they're caramelized alone before the mushrooms are cooked. The caramelization process should take about 15-20 minutes.
First put the sliced onions in a non-stick pan like cast iron with a drizzle of cooking oil or other fat. Heat the onions over high heat until they start to color, deglazing with a splash of water, stirring or tossing the pan, and repeating the process over and over.
The gradual deglazing of the pan coats the onions in their natural juices, slowly caramelizing and building flavor. Cook the pan until it's dry and begins to brown, add a splash of water, and repeat.
After about 15 minutes on high heat the onions will be a deep mahogany brown, rich and sweet. While some claim you need to cook caramelized onions for hours this will overcook them into a bowl of mushy pig slop. It's important the onions retain some of their texture.
Mushrooms
After the onions are cooked it's time for the mushrooms. To ensure the dish isn't oily, I like to cook the mushrooms with a wet saute first. I cut the mushrooms into bite sized pieces, add a splash of water, cover and cook until wilted and the pan is dry.
Finishing the Dish
Once the sliced mushrooms are wilted add a little oil and brown them. Next, season them with fresh chopped thyme (sage and rosemary in small amounts work too) mix in the caramelized onions and heat gently to let the flavors meld.
Finally, taste a bit and adjust the seasoning until it tastes good to you. From here the caramelized mushrooms and onions can be made in advance, or even frozen to use when you need them.
Serving Caramelized Mushrooms and Onions
- This is a great way to enhance mild tasting mushrooms like oyster mushrooms or late fall oysters, or a mix of mushrooms. Shiitake mushrooms are a good cultivated substitute but baby bella mushrooms or even basic white mushrooms can be ok too.
- For an even richer version use duck fat.
- This is one of the best toppings for burgers, like the homemade mushroom swiss burger of your dreams.
- Use it as a topping for cauliflower steak and vegetarian dishes.
- Use them as a caramelized onion focaccia topping.
- Put them on a grilled cheese sandwich.
- Toss with sauteed or steamed green beans.
- It goes without saying it's one of my favorite side dishes for steak of all kinds.
Related Posts
- Veal Liver with Mushrooms, Bacon and Onions
- Rich and Creamy Mushroom Dip
- Lebanese Dandelions with Caramelized Onions (Hindbeh)
Classic Caramelized Onions and Mushrooms
Equipment
- 1 large 10 inch skillet
- 1 wooden spoon
Ingredients
- 1 lb yellow sweet onions
- 1 lb mushrooms
- ½ teaspoon kosher salt
- 1 tablespoon chopped fresh thyme
- 1 cup water divided
- 3 tablespoons cooking oil, like grapeseed. light olive oil or duck fat divided
Instructions
Onions
- Cut the top and bottom from the onions and lay them cut side down. Cut the onions in half, then lay them cut side down on a cutting board. Peel off the skin and the first layer of flesh and discard, then thinly slice the onions.
- Heat 2 teaspoons of the cooking oil in a wide 10 inch skillet. Add the onions and cook on high heat, stirring regularly. When the onions start to brown around the edges, add about 2 tablespoons of water, stir to scrape up any brown bits, and continue to cook on high heat.
- Whenever the pan starts to dry out, add another splash of water and continue cooking until the onions are deep brown, stirring occasionally. This should take about 15 minutes. You will want to use a hood vent or open some windows.
- When the onions are caramelized, season them with a pinch of salt and reserve. Clean the pan out and get ready to cook the mushrooms.
Mushrooms
- Cut the mushrooms into bite sized pieces. You can be creative with the shapes here, some can be thickly sliced, mushroom caps can be quartered. Just keep in mind not to slice them too thin.
- Heat the mushrooms and ½ cup water in a covered 12 inch skillet or similar pan. Heat on medium heat until the water is evaporated and the pan is nearly dry, about 5 minutes.
- Add the remaining oil to the pan and turn the heat to medium high. Cook the mushrooms, stirring and tossing the pan regularly, seasoning with a pinch of salt until they’re starting to turn golden brown on the edges. This should take about 10-15 minutes.
Finishing
- When the mushrooms taste delicious, add the chopped thyme, stir and cook for a minute more.
- Add the reserved caramelized onions, mix, taste the seasoning for salt and pepper and adjust until it tastes good to you.
- From here the mushrooms and onions can be cooled and refrigerated until needed and made 3-4 days in advance.
Video
Notes
- Avoid the urge to be creative here. There is no need to add things like brown sugar, Worcestershire sauce, balsamic vinegar or wine to speed up the caramelization process. These change the flavor of the dish and make it taste strange.
- Cut the cook time in half by using two pans and cooking the onions and mushrooms at the same time.
Maíra
Hello Alan! How long can these mushrooms be stored in the refrigerator?
Alan Bergo
They'll be good for at least a week.
Dave Hedlund
I’ve found a record number of hens this year. A week ago I found a 9 pounder in perfect shape. Tonight I used the last pound for this recipe. Wow! The onion caramelization worked so well and the end result tastes soooo good. Thanks for another great recipe and a new technique for me. Amazing!!!
Alan Bergo
Hey thanks Dave.
Pixie
Through trial and error I've taught myself how to peel, slice and carmelize onions correctly. Not so with the mushrooms in this dish. I've tried cooking them with the onions, but it doesn't turn out well. Thanks for pointing me in the right direction...and saving my foraged treasure from ruination!
Alan Bergo
Hey thanks Pixie, I’m glad it was helpful!
Michelle Targonski
Perfect way to get my blood pumping for fall foods! This is incredible alone but I love this easy caramelization tutorial as a lead into lazanki! The addition of cabbage, dill and noodles with hens are very hearty and I appreciate your passion with onion prep! Thanks
Alan Bergo
Thanks for reminding me that’s a great idea! I need to link to my Lazanki recipe here.
David Britton
Alan -- not getting your onion-slicing manipulation sequence. ? 1. Guillotine top & bottom. 2. Remove outermost layer of flesh. 3. Halve stem to stern vertically. 4. Slice each half equatorially. 5. ?Rotate 90° - thinly slice across the ¼-section (but the first few cuts will be wonky on the curved outer face)? Just saw post of discovery of your video -- will watch 'n see.
Alan Bergo
Please watch the video it’s easier than trying to explain.
Cathy
Best way I’ve tried to carmelize onions and mushrooms! Fantastic turnout!!
Thank you so much for the straight forward approach and easy to follow step by step instructions!
Alan Bergo
Thanks Cathy, glad it worked for you.
Amy
I love the emphasis on cooking good ingredients simply and well. Nice to have an endorsement of not adding brown sugar or balsamic vinegar or a bunch of other deglazing options. Thanks for the cooking lesson!
Alan Bergo
Thanks Amy. Yes with so few ingredients the technique is the most important part.
Pam
Hi Alan,
Love your posts!
Somehow the onion cutting procedure isn't quite clear in my head. Perhaps a written step was missing?
The photo looks like you cut the onion from stem to bottom. Then you placed it cut side down. Then you cut each piece in half again. Is that correct?
Secondly, having belonged to a mushroom club in the past, we were always told to parboil this particular type of mushroom you are using, to remove bugs. They tend to love hiding in all the nooks and crannies. Indeed, I've found this to be true. Would this parboiling change the integrity of this dish in any way?
Alan Bergo
Yes, describing exactly how I cut the onions can be difficult to convey. That’s why there’s a video as well as images. If it isn’t clear, please watch the video. I show the onions cut in half a second time to make one inch slices, but it’s fine to leave them longer too, which is also shown in the beginning of the post in a separate image.
Laura Brown
How do you typically reheat these? In the microwave or in a pane with oil!
Alan Bergo
Don’t heat them with extra oil. I don’t use a microwave but that works just fine. Typically I just heat them in a pan on low and stir them occasionally. There’s enough moisture in the onions and mushrooms to steam it and heat through pretty quick.
EC
Sooo, I have always taken the skin off of onions, and the top one or two layers (usually two). I honestly don't remember how I do it after that, but my gut is telling me, not as you have instructed. I kept reading, hoping you had done a video, and to my delight, it was at the bottom. However I was doing it before, I will now be properly schooled, and for that I thank you!