It is made exceptionally tasty with small, tender, button mushrooms. I know they seem to be the most unloved of the mushroom family, but they are so good with onions over a perfectly cooked steak. But don't let that put you off, you could really do this with just about any mushroom you love.
Not counting the salt and pepper, this 4 ingredient side is the epitome of easy. You get so much flavor for such little effort, but one of the keys to the best flavor comes from the Vidalia onions. They are sweet yellow onions, famous in Georgia where I lived for my teen years, and they make this dish even better.
Then, of course, the butter and olive oil help draw out the flavor of the mushrooms and onions. I don't often use button mushrooms, because I am always reaching for something fancy these days, but they really evoked that nostalgic flavor and were so good for this basic side dish. Basic, but delicious!
Use the JUMP TO RECIPE button at the top of the post, or scroll to the bottom of the post to see the full recipe card with ingredient measurements and instructions.
I start by steaming the mushrooms in a super large skillet that has a lid. This gets the cooking started and all of the water leaching out of the mushrooms. They need about 5 minutes with the lid on over medium heat, then take the lid off and cook till there is no liquid in the pan.
Add the onions and butter and cook for about 10 minutes longer until the onions get soft and the mushrooms brown up a bit in the butter. High heat is key to getting caramelization and cooking them quickly.
You can get wild and add herbs or finish with some wine if you like, but I like the simplicity of the sweet onions, butter, mushrooms, salt, and pepper. It really makes for the best Sautéed Mushrooms and Onions.
Notes & Tips
Cook over medium-high heat for the best sear on the mushrooms and to evaporate away all of the water the let off, quickly.
Once you add the butter, turn the heat down to medium so it doesn't burn in the pan.
Use a really large pan with a lid. Having a lot of surface area allows the mushrooms to get caramelized and keeps them from steaming too much and getting mushy. The lid also gives the mushrooms a jumpstart on getting hot and letting their liquid out.
If you have it, and it is totally optional, you can finish the sautéed mushrooms and onions with a splash of white wine to add a hint of acidity to the final product.
I prefer button mushrooms for this recipe. It keeps it inexpensive and classic. Crimini mushrooms could also be used, or even portobello diced up.
Grapeseed or Avocado oil could be used in place of olive oil. They have a higher smoke point and a neutral flavor.
If you are dairy-free, use a plant-based butter to still help and achieve some of that creamy flavor the butter brings.
Vidalia Onions are THE BEST for this recipe, if you can not find them, any sweet yellow onion or even Texas 10/15 onions can be used. But the sweetest swap is red onion.