Classic Caramelized Onions and Mushrooms

A dish of caramelized onions and mushrooms next to a large mushroom on a cutting board.

5 from 7 votes

Rich caramelized onions and mushrooms scented with fresh herbs are the perfect side dish for steak, and one of the best burger toppings. Serves 4-6 as a side dish.

Prep Time15

Cook Time30

Total Time45

Course: Burger Topping, Condiment

Cuisine: American

Keyword: Caramelized mushrooms and onions, Carmelized onions and mushrooms, serving caramelized onions and mushrooms recipe

Servings: People

Calories: 131kcal

Author: Alan Bergo

Cost: 5

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.

Nutrition