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Home » Appetizers

French Onion Stuffed Mushrooms

A closeup photo of Tiffany holding a bouquet.
By Tiffany
Modified: Oct 13, 2026 · Published: Sep 29, 2026

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French onion stuffed mushrooms are filled with caramelized onions and melted Gruyère cheese for an easy bite-size appetizer packed with classic French onion flavor.

A white platter with French onion stuffed mushrooms on it.

Ingredients

  • Baby Bella Mushrooms
  • Olive Oil
  • Large Yellow Onions
  • Salt
  • Worcestershire Sauce
  • Fresh Thyme Leaves
  • Gruyère Cheese
  • Panko Breadcrumbs
  • Grated Parmesan Cheese
  • Olive Oil

How to Make French Onion Stuffed Mushrooms

  • Remove the mushroom stems and clean the mushroom caps with a damp paper towel. Place the mushroom caps on a parchment-lined baking sheet.
A white cutting board with mushroom caps and stems separated. It's sitting on a dark wood table.
  • Add olive oil to a skillet over medium-low heat. Add the onions and salt, and cook for 30-35 minutes, stirring occasionally, until deeply caramelized.
  • Stir in the Worcestershire sauce and thyme.
A black stovetop with a Hexclad skillet filled with onion slices.
A black stovetop with a Hexclad skillet with caramelized onions.
  • Preheat the oven to 375℉.
  • Fill each mushroom with caramelized onions, just to the brim of each “well”. Top with Gruyère cheese.
A corner of a baking sheet with mushrooms filled with caramelized onions.
A corner of a baking sheet is visible with mushrooms stuffed with caramelized onions topped with shredded gruyere cheese.
A round clear bowl of panko and a silver fork sitting on top of a blue and white striped napkin.
  • Mix panko, Parmesan, and olive oil. Sprinkle over the mushrooms.
  • Tip: If any of the onions underneath are not covered by cheese or panko, they risk burning as the mushrooms cook. Try to cover all of the onions.
A corner of a baking sheet with unbaked mushrooms filled with caramelized onions, shredded cheese, and breadcrumbs.
A corner of a baking sheet with baked French onion stuffed mushrooms.
  • Bake for 18 to 22 minutes, until the mushrooms are tender and the topping is golden.
A cream colored platter filled with french onion stuffed mushrooms.

FAQ

What kind of mushrooms are best for stuffed mushrooms?

White button mushrooms and cremini mushrooms both work well.

Can I make French onion stuffed mushrooms ahead of time?

Yes. Prepare and stuff the mushrooms, cover them, and refrigerate for up to 24 hours. Bake them just before serving for the best texture.

How do I keep stuffed mushrooms from getting watery?

Avoid soaking mushrooms in water when cleaning them because they will become waterlogged. It’s best to wipe them with a damp paper towel. It also helps not to overcrowd the baking dish so excess moisture can evaporate.

What cheese is best for French onion stuffed mushrooms?

Gruyère is the classic choice because it melts beautifully and gives the mushrooms that traditional French onion soup flavor. Swiss cheese, provolone, or a combination of cheeses can also work.

How do I store leftovers?

Store leftover stuffed mushrooms in an airtight container in the refrigerator for up to 3 days.

How do I reheat stuffed mushrooms?

Reheat them in a 350°F oven for about 8-12 minutes, or until warmed through. The oven or air fryer will give you a better texture than the microwave, which can make them soggier and chewier.

A white plate with a side view of French onion stuffed mushrooms and fresh thyme leaves.

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A white platter with French onion stuffed mushrooms on it.

French Onion Stuffed Mushrooms

Tiffany
French onion stuffed mushrooms are filled with caramelized onions and melted Gruyère cheese for an easy bite-size appetizer packed with classic French onion flavor.
No ratings yet
Print Recipe Pin Recipe
Prep Time 15 minutes mins
Cook Time 57 minutes mins
Total Time 1 hour hr 12 minutes mins
Course Appetizers
Cuisine American
Servings 20 Mushrooms
Calories 46 kcal

Equipment

  • Circulon Baking Sheets

Ingredients
  

  • 20 Baby Bella Mushrooms
  • 2 tablespoons Olive Oil
  • 2 Large Yellow Onions thinly sliced
  • ½ teaspoon Salt
  • 1 teaspoon Worcestershire Sauce
  • 1 teaspoon Fresh Thyme Leaves
  • ½ cup Shredded Gruyère Cheese
  • ¼ cup Panko Breadcrumbs
  • 2 tablespoons Grated Parmesan Cheese
  • 1 tablespoon Olive Oil

Instructions
 

  • Remove the mushroom stems and clean the mushroom caps with a damp paper towel. Place the mushroom caps on a parchment-lined baking sheet.
  • Add olive oil to a skillet over medium-low heat. Add the onions and salt, and cook for 30-35 minutes, stirring occasionally, until deeply caramelized.
  • Stir in the Worcestershire sauce and thyme.
  • Preheat the oven to 375℉.
  • Fill each mushroom with caramelized onions, just to the brim of each "well". Top with Gruyère Cheese.
  • Mix panko, Parmesan, and olive oil. Sprinkle over the mushrooms.
  • If any of the onions underneath are not covered by cheese or panko, they risk burning as the mushrooms cook. Try to cover all of the onions.
  • Bake for 18 to 22 minutes, until the mushrooms are tender and the topping is golden.

Nutrition

Calories: 46kcalCarbohydrates: 3gProtein: 2gFat: 3gSaturated Fat: 1gPolyunsaturated Fat: 0.3gMonounsaturated Fat: 2gCholesterol: 4mgSodium: 102mgPotassium: 114mgFiber: 0.4gSugar: 1gVitamin A: 41IUVitamin C: 1mgCalcium: 46mgIron: 0.2mg

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A closeup photo of Tiffany holding a bouquet.

Hello! I'm Tiffany.

I'm the recipe developer and food photographer behind Simply Happenings. I'm also a wife, mom to two adventurous little boys, registered nurse, and I live in the great Midwest. I like to feature high-protein recipes, one-pot meals, and delicious recipes you can cook with your favorite household appliances.

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