Ingredients:
2 tablespoons extra virgin olive oil
4 cups sliced onions (about 2-3 medium onions, sliced into 1/4-inch thick pieces)
1 tablespoon brown sugar
2 tablespoons balsamic vinegar
1/2 teaspoon salt
1/2 teaspoon pepper
8 ounces (1 sheet) frozen puff pastry, defrosted in the fridge for a couple of hours
2 ounces brie cheese, chilled, rind removed, and diced
2 ounces Gorgonzola or other blue cheese, diced
2 tablespoons fresh tarragon, chopped
Instructions:
Caramelize the Onions:
Heat the olive oil in a large pan over medium-high heat. Add the sliced onions and cook for about 10 minutes, stirring occasionally, until they begin to wilt and turn golden brown. Stir in the brown sugar, balsamic vinegar, salt, and pepper. Reduce the heat to low and continue cooking, uncovered, for 20-25 minutes, stirring occasionally, until the onions are deeply caramelized. If they start to dry out, add a splash of water. Once caramelized, set the onions aside to cool.
Prepare the Puff Pastry:
Preheat your oven to 400°F (200°C). Roll out the puff pastry into a rectangle about 10×14 inches (or any shape you prefer). Place the rolled-out pastry on a baking sheet lined with parchment paper. Use a fork to prick the pastry all over at 2-inch intervals to prevent it from puffing up too much during baking.
Assemble the Tart:
Evenly spread the cooled caramelized onions over the pastry, reaching all the way to the edges. Dot the surface with pieces of brie and Gorgonzola cheese, then sprinkle the chopped tarragon over the top.
Bake the Tart:
Place the assembled tart in the preheated oven and bake for 18-20 minutes, or until the cheese has melted and the puff pastry is golden and crispy.
Serve:
Allow the tart to cool for about 5 minutes before cutting it into wedges or squares. Serve warm and enjoy!