Name: French Onion Mushroom Tart
Total time: 1 h 30 min
Ingredients: 1 tart crust: You can use a store-bought crust for convenience, or opt for homemade if you’re feeling ambitious. A flaky, buttery crust is ideal.; 3 large onions, thinly sliced: These will be caramelized to bring out their natural sweetness.; 2 tablespoons olive oil: For sautéing the onions and mushrooms.; 2 tablespoons butter: Adds richness when cooking the onions and mushrooms.; 1 teaspoon sugar: Helps the onions caramelize faster and enhances their sweetness.; 1 teaspoon salt: To season both the onions and mushrooms.; 1/2 teaspoon pepper: For a bit of mild spice.; 1 pound mushrooms, sliced: Use cremini, button, or portobello for a robust flavor.; 2 cloves garlic, minced: Adds depth and a touch of aromatic spice.; 1 tablespoon fresh thyme, chopped (or 1 teaspoon dried thyme): Provides a classic herbaceous note that complements both onions and mushrooms.; 1 cup grated Gruyere cheese: This Swiss cheese adds a nutty, creamy texture that pairs well with the savory filling.; 1/2 cup heavy cream: For a rich, smooth custard.; 2 eggs: Bind the filling and give the tart a creamy texture.

Ingredients

Scale

1 tart crust: You can use a store-bought crust for convenience, or opt for homemade if you’re feeling ambitious. A flaky, buttery crust is ideal.
3 large onions, thinly sliced: These will be caramelized to bring out their natural sweetness.
2 tablespoons olive oil: For sautéing the onions and mushrooms.
2 tablespoons butter: Adds richness when cooking the onions and mushrooms.
1 teaspoon sugar: Helps the onions caramelize faster and enhances their sweetness.
1 teaspoon salt: To season both the onions and mushrooms.
1/2 teaspoon pepper: For a bit of mild spice.
1 pound mushrooms, sliced: Use cremini, button, or portobello for a robust flavor.
2 cloves garlic, minced: Adds depth and a touch of aromatic spice.
1 tablespoon fresh thyme, chopped (or 1 teaspoon dried thyme): Provides a classic herbaceous note that complements both onions and mushrooms.
1 cup grated Gruyere cheese: This Swiss cheese adds a nutty, creamy texture that pairs well with the savory filling.
1/2 cup heavy cream: For a rich, smooth custard.
2 eggs: Bind the filling and give the tart a creamy texture.

Instructions

1. Preheat the Oven

Set your oven to 375°F (190°C) to prepare for baking the tart. 🕑🔥

2. Caramelize the Onions

In a large skillet, heat 2 tablespoons of olive oil and 2 tablespoons of butter over medium heat.
Add the sliced onions, 1 teaspoon of sugar, salt, and pepper. Stir occasionally, allowing the onions to caramelize for about 30-40 minutes until they are soft, golden brown, and sweet. 🍳🧅
Once done, set them aside.

3. Cook the Mushrooms

Using the same skillet, add the sliced mushrooms and minced garlic.
Cook until the mushrooms have browned and released their moisture, about 10 minutes.
Stir in the fresh thyme and cook for another minute. Remove the skillet from heat and set aside. 🍄🌿

4. Prepare the Tart Crust

Roll out the tart crust and fit it into a tart pan. Use a fork to prick the bottom of the crust to prevent it from puffing up during baking.
Blind bake the crust for 10 minutes, which means pre-baking the crust without filling it. This helps ensure a crispy base. Once done, remove from the oven and let it cool slightly. 🥧🔪

5. Assemble the Tart

Spread the caramelized onions evenly over the bottom of the baked tart crust.
Layer the cooked mushrooms and garlic on top.
Sprinkle the grated Gruyere cheese evenly across the filling. 🧀🍄

6. Prepare the Custard

In a small bowl, whisk together 1/2 cup of heavy cream and 2 eggs until well combined. 🥄🥚
Pour this mixture over the tart filling, making sure it spreads evenly over the onions, mushrooms, and cheese.

7. Bake the Tart

Place the assembled tart into the preheated oven and bake for 25-30 minutes, or until the filling is set and the top is golden brown. The crust should be crisp and flaky, and the cheese melted and slightly bubbly. 🍽️🌟
Allow the tart to cool slightly before slicing.