Mediterranean French Onion & Mushroom Tart with Gruyère Cheese

🥧 Mediterranean French Onion & Mushroom Tart with Gruyère Cheese

A rustic and savory tart that brings together the sweet depth of caramelized onions, the umami of mushrooms, and the nutty richness of Gruyère cheese—all nestled in a flaky, buttery crust. Perfect for brunch, lunch, or a light dinner with a side salad.

🧾 Ingredients

For the Tart Crust (or substitute with store-bought shortcrust or puff pastry):

• 1¼ cups (160g) all-purpose flour
• ½ tsp salt
• 100g (7 tbsp) cold unsalted butter, cubed
• 3–4 tbsp ice water

For the Filling:

• 2 tbsp olive oil or unsalted butter
• 2 large onions, thinly sliced
• 2 cloves garlic, minced
• 1½ cups mushrooms (e.g., cremini, button, or mixed wild), sliced
• 1 tsp fresh thyme leaves (or ½ tsp dried thyme)
• Salt and black pepper, to taste
• 1 tsp balsamic vinegar (optional, for depth)
• ¾ cup grated Gruyère cheese
• 1 egg + 1 tbsp milk or cream (for egg wash, optional)

👩‍🍳 Instructions

1. Prepare the Crust:

1. In a bowl, combine flour and salt.
2. Cut in the cold butter with a pastry cutter or fingertips until mixture resembles coarse crumbs.
3. Gradually add ice water, 1 tbsp at a time, mixing just until dough comes together.
4. Form into a disk, wrap, and chill for 30 minutes.
5. Roll out on a floured surface and place into a tart pan (9-inch), trimming the edges.
6. Chill the crust again for 15 minutes while you preheat the oven to 375°F (190°C).

2. Caramelize the Onions & Cook Mushrooms:

1. In a large skillet, heat olive oil over medium heat.
2. Add sliced onions and a pinch of salt; cook slowly, stirring occasionally, for 20–25 minutes until deeply golden.
3. Add garlic, thyme, and mushrooms; cook another 8–10 minutes until mushrooms are soft and liquid evaporates.
4. Stir in balsamic vinegar if using, and adjust seasoning. Let cool slightly.

3. Assemble & Bake:

1. Spread onion-mushroom mixture evenly into the tart crust.
2. Sprinkle grated Gruyère cheese over the top.
3. Brush edges of crust with egg wash if desired.
4. Bake for 25–30 minutes until crust is golden and cheese is bubbling.
5. Let cool 5–10 minutes before slicing.

📝 Notes

• Store-bought puff pastry works great and saves time—just blind-bake slightly before adding the filling.
• Gruyère can be substituted with Emmental, Swiss, or Fontina.
• Add chopped sun-dried tomatoes or olives for extra Mediterranean flair.

💡 Tips

• Use a mandoline slicer for uniform onion slices.
• Chill the crust well before baking to prevent shrinkage.
• For a richer flavor, deglaze the onions with a splash of white wine.

🍽 Servings

• Makes 6 slices
• Ideal for 3–4 as a main dish or 6 as a side/starter.

🔢 Nutritional Info (Per Slice, Approx.)

• Calories: 310
• Protein: 9g
• Carbs: 23g
• Fat: 21g
• Fiber: 2g
• Calcium: 180mg

🌟 Benefits

• Rich in Flavor: Umami from mushrooms and Gruyère adds depth.
• Mediterranean-Inspired: Heart-healthy olive oil and antioxidant-rich onions.
• Versatile: Works as a light vegetarian meal or an elegant appetizer.

❓Q & A

Q: Can I make this tart ahead of time?
A: Yes! You can make and refrigerate the tart 1 day ahead. Reheat in the oven at 300°F for 10 minutes.

Q: Is it freezer-friendly?
A: Yes. Wrap the baked tart in foil and freeze. Reheat directly from frozen at 350°F for 20–25 minutes.

Q: What pairs well with this tart?
A: A fresh arugula salad with lemon vinaigrette or a glass of chilled white wine.