This French Onion and Mushroom Tart is a buttery, cheesy masterpiece that combines caramelized onions, earthy mushrooms, and nutty Gruyere cheese atop a flaky puff pastry crust. Perfect for appetizers, brunch, or a light dinner, this tart brings rustic elegance to any table. With its rich flavors and golden finish, it’s sure to impress!
Prep Time
- 20 minutes
Cook Time
- 45 minutes
Total Time
- 1 hour 5 minutes
Servings
- 4–6 servings
Ingredients
For the Tart:
- ¼ cup beef or vegetable stock
- 1¼ cups grated Gruyere cheese , divided
- 2 medium yellow onions, thinly sliced
- 3 tablespoons unsalted butter or ghee , divided
- ¼ cup dry sherry
- 1 large egg, whisked
- 1 tablespoon fresh thyme leaves , divided
- Salt and black pepper, to taste
- 2 cloves garlic, minced
- 1 sheet (14 oz) puff pastry, thawed
- 12 oz sliced cremini or shiitake mushrooms
- Parchment paper , for baking
Instructions
Step 1: Caramelize the Onions
- In a large skillet, melt 1½ tablespoons butter over medium heat.
- Add the sliced onions, season with salt and pepper, and cook for 20 minutes , stirring often, until soft, golden, and caramelized.
- Stir in the dry sherry and simmer until the liquid has almost completely evaporated.
- Add the beef or vegetable stock and cook until the mixture thickens slightly. Remove from heat and set aside.
Step 2: Cook the Mushrooms
- In the same skillet, melt the remaining 1½ tablespoons butter over medium-high heat.
- Add the sliced mushrooms, season with salt and pepper, and cook undisturbed for 2–3 minutes to allow them to brown.
- Stir and continue cooking for 5 more minutes , until tender and golden.
- Add the minced garlic and 1 teaspoon thyme , and cook for an additional 30 seconds . Transfer the mushrooms to a paper towel-lined plate to absorb excess moisture.
Step 3: Prep the Puff Pastry
- Preheat your oven to 200°C (400°F) .
- Roll out the thawed puff pastry sheet on a piece of parchment paper to approximately 10×13 inches .
- Using a sharp knife, lightly score a ½-inch border around the edges of the pastry (do not cut all the way through).
- Prick the center of the pastry with a fork to prevent it from puffing too much during baking.
Step 4: Assemble the Tart
- Sprinkle ¾ cup of the grated Gruyere cheese evenly over the center of the pastry, staying within the scored border.
- Spread the caramelized onions evenly over the cheese.
- Layer the cooked mushrooms on top of the onions.
- Sprinkle the remaining ½ cup of Gruyere cheese over the mushrooms.
- Brush the edges of the pastry with the whisked egg for a golden finish.
Step 5: Bake and Serve
- Bake the tart in the preheated oven for 20–25 minutes , or until the pastry is golden brown and puffed, and the cheese is melted and bubbly.
- Remove from the oven and let cool slightly.
- Sprinkle the remaining 1 teaspoon thyme over the tart for a fresh finishing touch.
- Slice and serve warm. Enjoy as an appetizer, side dish, or main course!
Pro Tips
- Make Ahead: Prepare the caramelized onions and mushrooms up to 2 days in advance . Store them in separate airtight containers in the refrigerator. Reheat before assembling the tart.
- Cheese Swap: Substitute Gruyere with Swiss or fontina cheese for a similar nutty flavor.
- Add Greens: Toss in a handful of baby spinach or arugula for a pop of color and freshness.
- Storage: Store leftovers in an airtight container in the refrigerator for up to 2 days . Reheat in the oven at 180°C (350°F) for 10 minutes to restore crispiness.
Nutrition Facts (Per Serving, based on 6 servings)
- Calories: ~350 kcal
- Protein: 12g
- Carbohydrates: 20g
- Fat: 25g
- Fiber: 3g
- Sugar: 6g
Note: Nutrition values are approximate and may vary based on specific ingredients used.
Why You’ll Love This Recipe
This French Onion and Mushroom Tart is a celebration of bold, savory flavors and textures. The sweetness of caramelized onions, the earthiness of mushrooms, and the nuttiness of Gruyere cheese create a harmonious blend that’s elevated by the buttery, flaky puff pastry. Whether you’re hosting a dinner party or simply craving something indulgent yet elegant, this tart delivers.
Ready to whip up this show-stopping dish? Grab your ingredients and get ready to enjoy a tart that’s buttery, cheesy, and utterly irresistible—it’s rustic charm on a plate!
