Description
Tender cremini mushroom caps piled high with deeply caramelized onions, melty Gruyère, and a crisp breadcrumb finish — all the cozy flavors of French onion soup in irresistible bite-sized form.
Ingredients
Units
Scale
Mushrooms
- 24 medium cremini mushrooms (about 1 lb; also called baby bellas)
- 2 tbsp extra-virgin olive oil (divided)
- 3/4 tsp salt (divided)
French Onion Filling & Topping
- 1 tbsp unsalted butter
- 2 large yellow onions (thinly sliced (about 6 cups))
- 1 tbsp sherry vinegar
- 1/2 cup unsalted beef broth
- 1 cup shredded Gruyère cheese
- 2 tbsp dry whole-wheat breadcrumbs
- fresh thyme leaves (for garnish (optional))
Instructions
- Prep and Pre‑Bake the Mushroom Caps: Preheat oven to 325°F (160°C). Remove and discard stems. Gently scrape out dark gills with a small spoon. Toss caps with 1 tbsp olive oil and 1/4 tsp salt on a large rimmed baking sheet. Arrange cap‑side up in a single layer and bake 10–15 minutes until tender and they release some liquid. Set aside.
- Caramelize the Onions: Heat butter and remaining 1 tbsp olive oil in a large skillet over medium heat. Add sliced onions and remaining 1/2 tsp salt. Cook, stirring frequently, about 40 minutes until deeply golden and significantly reduced.
- Deglaze and Build the Filling: Stir in sherry vinegar, scraping up browned bits; cook ~1 minute until evaporated. Add beef broth and cook, stirring often, ~3 minutes until most liquid evaporates and onions are glossy. Remove from heat.
- Fill the Caps: Arrange pre‑baked mushroom caps on the baking sheet. Fill each with about 2 teaspoons caramelized onions, pressing gently.
- Top & Bake: Sprinkle evenly with Gruyère, then lightly dust with breadcrumbs. Bake at 325°F (160°C) for ~10 minutes until cheese is melted and bubbly.
- Broil to Finish: Broil 3–5 minutes until cheese is deeply bubbly and breadcrumbs are golden. Garnish with thyme (optional) and serve immediately.
Notes
Make‑ahead: Caramelize onions up to 3 days in advance and refrigerate. Reheat before filling.
Variations: Swap beef broth for vegetable broth and use Swiss if Gruyère isn’t available.
Serving: Plan 2–3 bites per guest.
- Prep Time: 20 minutes
- Cook Time: 1 hour 10 minutes
- Category: Appetizer
- Cuisine: French
Nutrition
- Calories: 75
- Sugar: 2
- Fat: 5
- Saturated Fat: 2
- Carbohydrates: 4
- Fiber: 1
- Protein: 4
