How to Caramelize Onions and Mushrooms Together or Separately

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If you’re wondering how to caramelize onions and mushrooms, and concerned that it might be hard, don’t worry. It’s easy!

Caramelized Onions and Mushrooms Will Cook Way Down

Fresh mushrooms naturally reduce in size considerably when cooked due to a high moisture content.

Caramelized onions and mushrooms cook down further still, to only about 25% of the original raw ingredients. The water evaporates and the favors condense and concentrate, which is what make caramelized onions and mushrooms so delicious.

So six cups (three cups each) cook down to around 3/4 cup of each for 1.5 cups total caramelized onions and mushrooms!

So depending on your end usage and needs, you can increase (or decrease) quantities accordingly. For larger or more servings you’ll need to increase your beginning quantities.

You Can Cook the Onions and Mushrooms Together or Separately

If that amount ends up to be too much to cook the onions and mushrooms together in the largest pot you have to work with, then you can always batch these and caramelize the onions, remove from pan, then caramelize the mushrooms.

Caramelized onions and mushrooms cook down by up to 75% of the original raw ingredients.

Plan to Make More Than You Need

For anyone with a busy schedule (in other words, most everybody these days), you can save a lot of time by planning ahead. Whenever we cook, we double, triple or quadruple recipes, to save time. We don’t mind eating from the same pot of soup, or the same roasted veggies several times throughout the week, plus there are always ways to change things up.

Caramelize Extra Onions and Mushrooms

So when you caramelize onions and/or mushrooms, you may also want to cook more than you need and use them for other dishes.

There are many uses for caramelized onions and mushrooms, so having a little extra on hand for steak, burgers, soups, and omelettes, for instance, is a good “planned over” strategies.

Caramelized Onions and Mushrooms Recipe

Let us know how it goes for you and if you have any questions. We think you’ll be hooked on caramelized mushrooms and onions and looking for all kinds of ways to make use of this amazing concoction!

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Quick Caramelized Onions and Mushrooms Recipe

Remember, as indicated in the preceding paragraphs, caramelized onions and mushrooms cook down to only 25% of the measurements you start with.
This recipe of 6 cups of veggies (3 each of mushrooms and onions) cooks down to just 1.5 cups caramelized onions and mushrooms.
So for larger or more servings you'll need to increase your quantities.
Learn how to julienne onions.
Prep Time 5 minutes
Cook Time 10 minutes
Total Time 15 minutes
Servings 1 .5 cups


  • 4 tablespoons butter or oil or half oil and half butter
  • 2 large yellow onion ~3 cups
  • 12 oz. mushrooms cleaned and sliced (~3 cups)
  • 1/2 teaspoon salt or to taste


  • JULIENNE onions (to thinly slice)
  • ADD butter and/or oil to sauté pan on medium to medium high heat
  • MELT butter and let it start to brown slightly, then, immediately add onions, mushrooms and salt. (If the quantity is too large for your pot, you can first caramelize he onions, remove from pan, then caramelize the mushrooms.
  • COOK sliced onions and mushrooms in butter in a large sauté pan, dutch oven or wok.
  • COVER with lid to help expedite the softening of the onions.
  • TIMER – Set timer for 1 or 2 minutes to stir. You want your pan to brown without burning.
  • STIR – Once pan begins to brown then stir up the "fond" (brown bits) in the pan.
  • LOOSEN the fond with a splash of water or white cooking wine and scrape it from the pant with flat edge of wooden spatula and stir it into the onions
  • COVER and repeat the process until onions are nicely caramelized in about 10-20 minutes, (depending on if you have to separate the onions and mushrooms).
Tried this recipe?Let us know how it was!

See also, how to caramelize onions faster, as well as this delicious green bean soup with caramelized onions and mushrooms.

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