French Onion Stuffed Mushrooms are everything you love about the classic soup—sweet caramelized onions, melty cheese, and savory richness—tucked into a bite-sized appetizer. These little guys are warm, gooey, and packed with flavor, making them perfect for any gathering or just a cozy night in.

French Onion Stuffed Mushrooms on a brown surface.

They’re surprisingly easy to pull together, and the slow-cooked onions give them that deep, comforting taste that feels way fancier than the effort involved. Pop them in the oven and let the cheesy magic happen.

The first time I made these, I was hosting a small holiday get-together and wanted something a little fancier than the usual chips and dip. I didn’t expect them to be such a hit, but they disappeared faster than anything else on the table. Now, they’re one of my go-to appetizers whenever I want to impress without a ton of effort.

Whether you serve them for the holidays, a dinner party, or just because you deserve a treat, these French Onion Stuffed Mushrooms are guaranteed to disappear fast.

Why You’ll Love This Recipe

Big flavor in a small bite: Caramelized onions and gooey cheese pack a punch in every mushroom cap.
Perfect for entertaining: These look impressive but are easy to make ahead and pop in the oven when guests arrive.
Comfort food vibes: All the cozy goodness of French onion soup, minus the bowl and spoon.
Simple ingredients: You likely already have most of what you need in your kitchen.
Crowd-pleaser: Even people who claim they don’t like mushrooms tend to go back for seconds.
Versatile: Great as a holiday appetizer, party snack, or even a side dish with steak or roast chicken.

Ingredients

The full printable recipe card with measurements and instructions is found at the bottom of the post.

White button mushrooms: Choose ones that are firm and roughly the same size so they cook evenly and look great on a platter.
Yellow onions: These are perfect for caramelizing thanks to their natural sweetness. Slice them thin for quicker, more even cooking.
Salted butter: Adds richness and helps the onions break down into that deep golden goodness.
Fresh thyme: A little goes a long way in adding earthy flavor. Strip the leaves from the stems for easy mixing.
Swiss cheese: Melts beautifully and adds that signature French onion tang. Gruyère is a great substitute if you want to get fancy.
Garlic: Adds a mellow kick of flavor once softened—don’t skip it!
Beef broth: Enhances the savory, soup-inspired flavor. You can swap in veggie broth for a vegetarian version.

How to Make French Onion Stuffed Mushrooms

Step One: Melt butter in a large skillet over medium heat. Add onions to the pan and caramelize for 15 minutes. Add in garlic cloves and continue to caramelize for an additional 3 to 5 minutes.
Step Two: Stir in beef broth and cook for two more minutes.

Collage of caramelizing onions in a pan.

Step Three: Add onion mixture to a medium bowl and add thyme. Add a teaspoon of filling to each mushroom and arrange them on a baking sheet. Top with cheese and garnish with a bit of fresh thyme.
Step Four: Bake for 20 minutes in a 350°F oven.

Collage of stuffing and baking the mushrooms.

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What to Serve With Them

Charcuterie board: These mushrooms pair beautifully with cured meats, cheeses, and olives.
Crostini or toasted baguette slices: Add a bit of crunch to contrast the soft, cheesy filling.
Green salad: Something light and fresh balances out the richness.
Steak or roast chicken: Makes a delicious starter or side dish for a hearty main.
Pasta dishes: Especially creamy or garlic-based pastas that complement the savory flavor.
Soup: Try pairing with a light broth-based soup or even a small cup of—you guessed it—French onion soup.
Holiday appetizer spread: Add to a mix of bites like stuffed mini peppers, meatballs, or pinwheels.

Variations and Substitutions

Make it vegetarian: Swap the beef broth for vegetable broth without losing that savory depth.
Try different cheese: Gruyère cheese, provolone, or even mozzarella can stand in for Swiss if that’s what you have on hand.
Add breadcrumbs: Sprinkle a little seasoned panko on top before baking for extra crunch.
Use baby bella or cremini mushrooms. They are slightly meatier and more flavorful than white button mushrooms, but they are just as easy to stuff.
Boost the herbs: Add a touch of rosemary or parsley if you want to switch up the flavor profile. If you don’t have fresh thyme leaves, use ½ teaspoon dried thyme.
Swap butter for olive oil: Use ¼ cup of olive oil in place of the butter for caramelizing the onions. It lightens up the dish while still giving great flavor.
Use unsalted butter: If you prefer more control over the saltiness, unsalted butter is a great option. Just taste and season with salt and black pepper as needed.
Add Worcestershire sauce: Stir in 1 to 2 teaspoons with the broth for extra depth and umami richness.
Finish under the broiler: Pop the mushrooms under the broiler for 1–2 minutes after baking to get that irresistible golden, bubbly cheese top. Keep a close eye so they don’t burn!
Make it a meal: Double the filling and use large portobello mushroom caps for a satisfying vegetarian main dish.

Storage Instructions

Refrigerate leftovers: Store any leftover stuffed mushrooms in an airtight container in the fridge for up to 3 days.
Reheat gently: Warm them in the oven at 300°F until heated, about 10–15 minutes. This helps keep the mushrooms from getting soggy.
Avoid the microwave: It can make the mushrooms rubbery and the filling watery.
Not freezer-friendly: These are best enjoyed fresh, as the texture of the mushrooms doesn’t hold up well after freezing.

Recipe Tips and Tricks

Don’t rush the onions: Low and slow is key to getting that deep, caramelized flavor. Give them time to get golden and sweet.
Use a spoon or melon baller: To gently scoop out a bit of the mushroom center and make more room for the filling.
Pat mushrooms dry: After cleaning, make sure they’re dry to avoid extra moisture during baking.
Shred your own cheese: It melts better than pre-shredded and gives you a creamier finish.
Line your baking sheet: Use parchment paper for easy cleanup and to prevent sticking.
Prep ahead: You can make the filling a day in advance and stuff the mushrooms right before baking.
Garnish just before serving: A sprinkle of fresh thyme adds a pop of color and flavor when they come out of the oven.

Easy Appetizers

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