French

Gruyère and Caramelised Onion Tart

Gruyère and Caramelised Onion Tart
This exquisite tart combines the nutty depth of aged Gruyère cheese with the rich, melt-in-your-mouth sweetness of slow-cooked balsamic onions. Nestled in a crisp, golden-brown puff pastry crust, it offers a sophisticated balance of savory and sweet flavors that is perfect for brunch or a dinner party starter.

Prep

20m

Cook

45m

Serves

6


1 Ingredients

Qty Ingredient
1 package 320 g All-butter puff pastry sheet
3 large 750 g Large yellow onions, thinly sliced
2 tbsp 30 g Unsalted butter
1 tbsp 15 ml Extra virgin olive oil
1 tbsp 15 ml Balsamic vinegar
1 tsp 2 g Fresh thyme leaves
1.5 cups 150 g Gruyère cheese, grated
1 large 50 g Egg (for egg wash)
0.5 tsp 2 g Salt and freshly ground black pepper

2 Method

1

Step 1. Melt the butter and olive oil in a large skillet over medium-low heat. Add the sliced onions with a pinch of salt.

2

Step 2. Cook the onions slowly for 25-30 minutes, stirring occasionally, until they are soft and deep golden brown. If they start to stick, add a splash of water.

3

Step 3. Stir in the balsamic vinegar and thyme, cooking for another 2 minutes until the liquid has evaporated. Remove from heat and let cool slightly.

4

Step 4. Preheat your oven to 200°C (400°F). Line a baking tray with parchment paper.

5

Step 5. Unroll the puff pastry onto the tray. Use a sharp knife to lightly score a 1-inch border around the edge, being careful not to cut all the way through.

6

Step 6. Prick the center area of the pastry (inside the border) several times with a fork to prevent it from rising too much.

7

Step 7. Spread the caramelised onions evenly over the center of the pastry. Sprinkle the grated Gruyère cheese generously over the onions.

8

Step 8. Brush the border of the pastry with the beaten egg wash. Bake for 15-20 minutes, or until the pastry is puffed and golden and the cheese is bubbly.

9

Step 9. Let cool for 5 minutes before slicing. Garnish with extra fresh thyme if desired.

💡 Chef's Tips

  • ·

    Patience is key for the onions; low and slow heat ensures they caramelise without burning.

  • ·

    Ensure your puff pastry is very cold when it goes into the oven for the best rise and flakiness.

  • ·

    For a deeper flavor, use a cave-aged Gruyère which has more crystalline texture and nuttiness.

  • ·

    If you want a 'blind baked' crispier base, you can pre-bake the pastry for 8 minutes with weights before adding the toppings.

? FAQ

Can I make this tart ahead of time?
Yes, you can prepare the caramelised onions up to 2 days in advance. The assembled tart is best served fresh, but can be reheated in a 180°C (350°F) oven for 5-10 minutes to restore crispness.
What can I use instead of Gruyère?
Comté, Emmental, or a sharp Fontina are excellent substitutes that melt well and offer a similar flavor profile.
How do I prevent a soggy bottom?
Ensure the onions are not too wet when you spread them on the pastry. Also, baking on a preheated baking stone or a heavy-duty baking sheet helps transfer heat quickly to the bottom crust.
Can I add other toppings?
Absolutely. Sautéed mushrooms, toasted walnuts, or a handful of fresh arugula added after baking all complement the onion and Gruyère beautifully.

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