Everyday French Onion Mushrooms A simple appetizer that can be made with pantry ingredients and features caramelized onions, swiss cheese, and portabellas

Everyday French Onion Mushrooms

by Michele Pesula Kuegler | October 19th, 2020 | Appetizers, Recipes, Tapas Monday

Make it from your pantry French onion filling is what your portabella needs.

portabella topped with caramelized onion and swiss cheese
portabella topped with caramelized onion and swiss cheese

Everyday French Onion Mushrooms

Michele Pesula Kuegler

Prep Time 10 mins
Cook Time 30 mins
Total Time 45 mins

Course Appetizer

Servings 4



  • 4 portabella mushrooms
  • 1/2 tablespoon olive oil
  • 1/2 tablespoon butter
  • 2 cups sliced sweet onion
  • 1 teaspoon granulated white sugar optional
  • 1 tablespoon fresh thyme*
  • 3/4 cup beef broth
  • Black pepper
  • 4 slices swiss cheese from the deli



  • Preheat oven to 425°F.
  • Remove mushroom stems and a small amount of gills with a spoon to provide more area to hold filling.
  • Brush both sides of mushrooms lightly with olive oil.
  • Place mushrooms cap side down on a rimmed baking sheet.
  • Bake for 8 minutes; flip and bake for an additional 4-6 minutes or until tender.
  • Remove from oven, and place caps gill side down on a paper towel-lined plate.
  • While mushrooms bake, melt butter in a large frying pan over medium heat.
  • Add onions, reduce heat to medium-low, and sauté for 20-25 minutes or until golden brown.
  • Preheat broiler.
  • Add sugar, thyme, and broth, and increase heat to medium.
  • Sauté for another 5 minutes or until all liquid is absorbed.
  • Place mushrooms cap side down on a rimmed baking sheet, and divide onion mixture among the mushrooms.
  • Top each with a slice of swiss cheese.
  • Place baking sheet on the upper rack of the oven, and broil for 30-60 seconds or until cheese melts.


Can be replaced with 1 teaspoon dried thyme

Keyword stuffed mushrooms

This is not my first time making French Onion Mushrooms. No, my original French Onion Mushroom recipe was created in 2016. It was a delicious recipe, but it requires ingredients that may not be kept in your pantry. On Wednesday I’ll be sharing it again, but for now I want to focus on the new version.

Today I have what I originally was going to call French Onion Mushrooms Redone. However, https://thinktasty1.wpengine.com/special-occasion-french-onion-mushrooms/when I thought about the differences in the recipes, I decided that this version is more of an everyday version than a 2.0 version. This recipe is meant to be made with ingredients that you already have on hand. Let’s take a peek:

  • olive oil- always on hand
  • butter- always on hand
  • sweet onion- always on hand but you could substitute a regular yellow onion, if needed
  • white sugar- always on hand
  • fresh/dried thyme- probably on hand
  • beef broth- that or some other broth or bouillon is probably on hand
  • black pepper- always on hand
portabella topped with caramelized onion and swiss cheese

The only two items you need to buy are the portabellas and the swiss cheese. I don’t say this as someone with a highly stocked kitchen. I spent the past seven months living in a long-term condo in Hot Springs, so I had a kitchen at about 50% of its usual items. Plus, this recipe is flexible. If you don’t have thyme, you could try a different herb, such as thyme or sage. You also could replace the beef broth with chicken, but it will have a little less flavor in the final product.

Of course, with a simpler set of ingredients you will have a simpler dish, which gives it another reason to be considered everyday. You still have all the sweetness and texture of the caramelized onion, but its overall flavor isn’t as rich and robust. I don’t consider that to be a bad thing.

You could compare the two versions of French onion mushrooms with a burger. Sometimes you want a simple hamburger, maybe with just a little mustard and ketchup. That’s an everyday burger. Other times you want a burger with truffle mayonnaise, caramelized onions, and gruyère. That’s a special occasion burger. Regardless to their differences, you enjoy them both.

portabella topped with caramelized onion and swiss cheese

Try this recipe for a quick weeknight appetizer, or serve with a salad and some good bread for your main meal. Either way, it’ll be quick to make and will satisfy your craving for French onion anything.

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