This French Onion and Mushroom Tart is a masterpiece of flavor and texture, combining buttery puff pastry, sweet caramelized onions, earthy mushrooms, and nutty Gruyere cheese. Perfect for brunch, appetizers, or a cozy dinner, this tart is as elegant as it is comforting. With its golden crust and rich toppings, it’s sure to impress!
📋 Ingredients
- 1 sheet puff pastry (14 oz), thawed
- 12 oz sliced shiitake or cremini mushrooms
- 2 medium yellow onions , thinly sliced
- 1¼ cups grated Gruyere cheese
- ¼ cup dry sherry
- ¼ cup beef or vegetable stock
- 3 tbsp ghee or unsalted butter , divided
- 2 cloves garlic , minced
- 1 tbsp fresh thyme leaves , divided (about 1 tsp reserved for garnish)
- 1 large egg , whisked
- Salt and pepper , to taste
- Parchment paper
👩🍳 Instructions
Step 1: Caramelize the Onions
- In a large skillet, melt 1½ tbsp ghee over medium heat . Add the thinly sliced onions and sauté for 20 minutes , stirring occasionally, until deeply caramelized and golden brown.
- Pour in the dry sherry and cook for 2–3 minutes , scraping up any browned bits from the bottom of the pan.
- Stir in the beef or vegetable stock and continue cooking until nearly evaporated, about 5 minutes . Season with salt and pepper to taste. Remove from heat and set aside.
Step 2: Sauté the Mushrooms
- In the same skillet, heat the remaining 1½ tbsp ghee over medium-high heat .
- Add the sliced mushrooms and let them cook undisturbed for 2 minutes to develop color. Stir and continue cooking for 5–7 minutes , until tender and golden.
- Stir in the minced garlic and 1 tsp thyme . Cook for 30 seconds , until fragrant. Transfer the mushrooms to a paper towel–lined plate to absorb excess moisture.
Step 3: Prep the Puff Pastry
- Preheat your oven to 400°F (200°C) . Line a baking sheet with parchment paper .
- Roll out the thawed puff pastry on the parchment to form a rectangle approximately 10×13 inches .
- Use a sharp knife to 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 all over with a fork to prevent it from puffing too much during baking.
Step 4: Assemble the Tart
- Sprinkle ¾ cup of grated Gruyere cheese evenly inside the scored border of the puff pastry.
- Spread the caramelized onions over the cheese, followed by the sautéed mushrooms .
- Top with the remaining ½ cup of Gruyere cheese .
- Brush the edges of the puff pastry with the whisked egg for a golden finish.
Step 5: Bake and Finish
- Bake the tart in the preheated oven for 26–30 minutes , or until the pastry is golden brown and the cheese is bubbly and slightly browned.
- Remove the tart from the oven and let it rest for 10 minutes before slicing.
- Garnish with the remaining 1 tsp fresh thyme leaves and serve warm.
Tips for Success
- Onion Prep: Low and slow is key to caramelizing onions. Don’t rush the process—let them develop their natural sweetness.
- Mushroom Variations: Use a mix of wild mushrooms like shiitake, cremini, and oyster for added depth of flavor.
- Cheese Swap: If Gruyere isn’t available, substitute with Swiss or fontina cheese for a similar nutty, melty texture.
- Make Ahead: Assemble the tart (without baking) up to 1 day in advance and refrigerate. Bake just before serving for best results.
- Storage: Store leftovers in an airtight container in the refrigerator for up to 2–3 days . Reheat in the oven at 350°F (175°C) for 10–15 minutes to restore crispiness.
Why You’ll Love This Recipe
This French Onion and Mushroom Tart is a celebration of flavors and textures. The buttery puff pastry provides a crisp base, while the caramelized onions add sweetness and depth. The earthy mushrooms and nutty Gruyere cheese create a savory, umami-rich topping that’s irresistible. Whether you’re serving it as an appetizer, brunch centerpiece, or light dinner, this tart is guaranteed to impress. Dive into this golden, cheesy delight and let it become a staple in your recipe collection!
⏱ Time
- Preparation Time: 20 minutes
- Cooking Time: 40 minutes
- Total Time: ~1 hour
🍽 Servings:
6–8 servings
🔥 Calories (Approximate):
~350 kcal per serving (varies based on portion size)
