Steps
1. Preheat the oven to 200°C (390°F).
2. Heat olive oil in a pan over medium heat.
3. Add sliced onions and cook slowly for about 15 minutes until caramelized, stirring occasionally.
4. Add balsamic vinegar, salt, pepper, and thyme; cook for another 2 minutes. Remove from heat.
5. Roll out the puff pastry on a baking tray lined with parchment paper.
6. Spread the caramelized onions evenly over the pastry, leaving a 1cm border.
7. Crumble goat cheese over the onions.
8. Fold the edges of the pastry slightly over the filling to create a border.
9. Bake for 20 minutes or until the pastry is golden brown and crisp.
10. Let cool slightly before serving.