French Onion Stuffed Mushrooms
French onion stuffed mushrooms with caramelized onions, Gruyère, and crispy Parmesan-panko. These are an irresistible bite-sized appetizer!
Servings: 12 mushrooms
Calories: 100kcal
Ingredients
- 1 pint baby portobello mushrooms about 12–14 medium mushrooms
- 2 medium yellow onions diced
- 2 tablespoons unsalted butter
- 3 tablespoons olive oil divided, plus more as needed
- 2 garlic cloves minced
- 4 sprigs fresh thyme leaves removed (plus extra for garnish)
- Salt and freshly ground black pepper to taste
- 2 tablespoons marsala wine or sherry, cognac, or red wine
- ½ cup shredded Gruyère cheese
- ¼ cup panko breadcrumbs
- 2 tablespoons grated Parmesan cheese
Instructions
- Preheat the oven to 350 degrees Fahrenheit. Line a baking sheet with parchment paper.
- Prep the mushrooms: Remove stems, finely chop them, and set aside. Place mushroom caps on the baking sheet, stem side up, drizzle lightly with olive oil, and season with salt and pepper. Bake for 10 minutes. Drain off any liquid and set aside to cool slightly.
- Caramelize the onions: In a large skillet, heat butter and 1 tablespoon olive oil over medium heat. Add the diced onions, season lightly with salt, and cook slowly for 45 to 50 minutes, stirring occasionally. Keep the skillet covered for part of the cooking time to trap moisture. The onions should become deeply golden and jammy.
- Add stems and aromatics: Stir in the chopped mushroom stems and cook for 2 minutes until softened. Add the garlic, thyme and saute for another 30 seconds to 1 minute.
- Deglaze: Carefully pour in the marsala wine and cook until most of the liquid has evaporated and the mixture is rich and concentrated. Taste and adjust seasoning and remove from heat.
- Make the breadcrumb topping: In a small bowl, combine the panko breadcrumbs, Parmesan and parsley. Drizzle with 1 to 2 tablespoons olive oil and toss until lightly coated.
- Assemble the mushrooms: Spoon the onion mixture into each mushroom cap. Sprinkle with shredded Gruyère, then top with the breadcrumb-Parmesan mixture.
- Bake: Return the mushrooms to the oven and bake for 10-12 minutes, until the cheese is melted and the breadcrumbs are golden. For extra crispness, broil for 1 minute at the end, watching closely.
- Serve: Garnish with fresh thyme leaves and an extra sprinkle of Parmesan. Serve warm.
Notes
- Clean mushrooms – Wipe with a damp cloth, not water.
- Par-bake the mushrooms – Helps release liquid; drain before stuffing.
- Slow-cook onions – Caramelize 45–50 minutes for best flavor.
- Dice onions – Fits better in mushroom caps.
- Toast panko – Toss with olive oil for golden crunch.
- Make ahead – Stuff up to 2 days early; add cheese/topping before baking.
Nutrition
Calories: 100kcal | Carbohydrates: 5g | Protein: 3g | Fat: 8g | Saturated Fat: 3g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 4g | Trans Fat: 0.1g | Cholesterol: 12mg | Sodium: 67mg | Potassium: 219mg | Fiber: 1g | Sugar: 2g | Vitamin A: 134IU | Vitamin C: 2mg | Calcium: 80mg | Iron: 0.4mg