French Onion Mushroom Tart

If you’re a fan of the rich, savory flavors of French onion soup and the earthy taste of mushrooms, this French Onion Mushroom Tart is going to be your new favorite. This tart combines the sweet caramelized onions, sautéed mushrooms, and gooey melted cheese in a flaky puff pastry crust that’s pure comfort in every bite. It’s perfect for brunch, lunch, or even as a light dinner, served with a fresh green salad.

This tart is all about those deep, comforting flavors that make you want to curl up with a good book and a glass of wine. The onions are cooked low and slow until they’re sweet and golden, the mushrooms add a meaty, umami kick, and the puff pastry provides the perfect crispy, buttery base. It’s a dish that feels fancy but is surprisingly easy to make!

Recipe Summary

The French Onion Mushroom Tart is an elegant and comforting dish that pairs perfectly with a light salad or a glass of white wine. The key to this recipe is the slow caramelization of the onions, which brings out their natural sweetness, and the sautéed mushrooms that add a depth of flavor. The tart is baked to golden perfection with a layer of melted Gruyère cheese that ties everything together.

This tart is ideal for impressing guests or simply treating yourself to a restaurant-quality meal at home. It’s versatile enough to serve as an appetizer, a main course, or even a delicious side dish.

Exciting Story

This tart has become a beloved weekend ritual in our house. My husband and I first discovered our love for French onion soup during a trip to Paris, and we’ve been trying to recreate those flavors ever since. When I came up with this French Onion Mushroom Tart, it was an instant hit. The combination of caramelized onions and mushrooms on a flaky crust reminded us of cozy French bistros. Now, we make it whenever we need a little taste of France at home. Paired with a crisp salad and a glass of wine, it’s the perfect way to bring a touch of Paris to our dining table.

Why This French Onion Mushroom Tart?

• Rich, Savory Flavors: Caramelized onions, sautéed mushrooms, and melted cheese create a deliciously savory tart.
• Elegant Yet Easy: Looks and tastes like a gourmet dish but is simple enough to make at home.
• Versatile: Perfect for brunch, lunch, or dinner, and pairs well with a variety of sides.
• Comfort Food: The flavors are warm, comforting, and perfect for any time of year.

How to Make French Onion Mushroom Tart

Step 1: Caramelize the Onions
Start by heating the butter and olive oil in a large skillet over medium-low heat. Add the sliced onions and cook, stirring occasionally, for about 30 minutes, or until the onions are golden brown and caramelized. Add the sugar, salt, and pepper halfway through cooking to help with the caramelization process. Set the onions aside.

Step 2: Sauté the Mushrooms
In the same skillet, add a little more butter if needed and increase the heat to medium. Add the sliced mushrooms and sauté until they’re golden brown and any liquid has evaporated, about 10 minutes. Stir in the fresh thyme if using, and set the mushrooms aside.

Step 3: Prepare the Puff Pastry
Preheat your oven to 400°F (200°C). Roll out the puff pastry on a lightly floured surface into a rectangle that fits your baking sheet. Place the pastry on a parchment-lined baking sheet and score a 1-inch border around the edges with a sharp knife (don’t cut all the way through). This will create a raised edge as the tart bakes.

Step 4: Assemble the Tart
Spread the caramelized onions evenly over the puff pastry, staying within the scored border. Top with the sautéed mushrooms, then sprinkle the Gruyère and Parmesan cheese over the top. Brush the edges of the pastry with the beaten egg for a golden finish.

Step 5: Bake the Tart
Bake in the preheated oven for 20-25 minutes, or until the pastry is puffed and golden brown and the cheese is melted and bubbly. Allow the tart to cool slightly before slicing and serving.

Tips

• Time Your Onions: Caramelizing onions takes time—don’t rush it! Low and slow is the key to getting them sweet and golden.
• Keep the Pastry Cold: Cold puff pastry puffs up better, so keep it in the fridge until you’re ready to use it.
• Add a Touch of Wine: For an extra layer of flavor, deglaze the pan with a splash of white wine after cooking the onions.

Substitutions and Variations

• Cheese Options: Try using Swiss, Fontina, or even a sharp cheddar instead of Gruyère.
• Different Mushrooms: Mix and match different types of mushrooms for varied textures and flavors.
• Herb Swap: Substitute thyme with rosemary, sage, or even a sprinkle of herbes de Provence.

Make a Healthier Version

• Whole Wheat Pastry: Use whole wheat puff pastry for added fiber.
• Lower the Fat: Reduce the amount of cheese, or use a lower-fat cheese to lighten up the tart.
• Skip the Sugar: Leave out the sugar in the onions for a less sweet, more savory flavor.

Closing

And there you have it! A delightful French Onion Mushroom Tart that brings a little taste of France to your kitchen. This tart is a beautiful balance of rich, savory flavors and crispy, buttery pastry. Serve it up for brunch, lunch, or a light dinner, and don’t forget to explore our other French-inspired recipes for more culinary inspiration!

Frequently Asked Questions

Can I make this tart ahead of time?
Yes, you can prepare the onions and mushrooms ahead of time and assemble the tart just before baking.

What’s the best way to reheat leftovers?
Reheat leftover tart in the oven at 350°F (175°C) until warmed through to keep the pastry crispy.

Can I use a different type of pastry?
Yes, shortcrust pastry or even a homemade tart dough would work well.

How do I prevent the pastry from getting soggy?
Make sure to cook the onions and mushrooms until most of the liquid has evaporated before adding them to the tart.

What should I serve with this tart?
A light green salad with a vinaigrette pairs beautifully with this rich tart.

Can I freeze the tart?
You can freeze the assembled tart before baking, then bake from frozen, adding a few extra minutes to the baking time.