In a food processor, place flour, cubed butter and salt. Pulse about 10 times. Add ½ cup water and pulse until the dough forms into a ball.
Add more water if needed.
Transfer to a floured surface and knead a few times. Using a lightly floured rolling pin roll the dough into a 10x15-inch rectangle. Fold the dough three times in half, wrap with a plastic wrap and refrigerate for at least one hour. The pastry should be cold but easy to work with.
Prepare the filling
Heat oil in a large pan over medium heat. Add onions and cook for about 8 minutes until starting to brown. Stir in Domino® Light Brown Sugar, balsamic vinegar, thyme, and salt. Cook for additional 15 minutes or until caramelized. Season with black pepper. Let cool to room temperature.
Assemble the pastries
Meanwhile, preheat oven to 400 degrees Fahrenheit. Make an egg wash by whisking an egg in a small bowl.
Roll puff pastry into a 10x15-inch rectangle on a floured surface. Cut into 9 squares. Place each piece onto a baking sheet lined with parchment paper about 2 inches apart. Top each piece with caramelized onions and diced brie. Brush the edges with egg wash. Bake for 15-20 minutes until the cheese has melted and pastry is golden brown.
To save time, you can use a pre-made thawed puff pastry. Puff pastry needs to be kept cold for the best results, make sure to work quickly!
The egg wash makes the tarts more golden once cooked. You can omit it if needed.
Tarts can be reheated at 350 degrees Fahrenheit for about 8-10 minutes.
The recipe is perfect for parties and can be double or tripled to feed the crowd!
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