Directions

1. To make the rough puff pastry, add the flour, 1 teaspoon of salt, and 120g of butter (slightly softened but not at room temperature) to a bowl.
2. Using your hands, crumble the butter into the flour. Aim to keep some larger lumps of butter. Gradually add ice-cold water, one tablespoon at a time, mixing until the dough just comes together. Then wrap it in cling film, shape it into a disc, and chill in the fridge for 1 hour.
3. After chilling, roll out the dough to approximately 20cm x 10cm (about 8" x 4"). Fold it over itself like a letter going into an envelope, press firmly, cover, and return to the fridge for another hour.
4. Repeat the rolling and folding process three more times.
5. Preheat the oven to 160°C (320°F).
6. Peel the onions, keeping the ends intact, and cut them in half. In a cast-iron pan over medium heat, add the remaining 80g of butter and the olive oil. Sprinkle it with salt and place the onions face down in the pan.
7. Sprinkle over the brown sugar and thyme leaves, and pour over the balsamic glaze.
8. Cook over medium-low heat for 10 minutes.
9. Meanwhile, roll out the pastry to 0.5cm (about 0.2") thick and cut a disc slightly larger than the pan.
10. Place the pastry disc over the onions, tucking the edges down the sides. Score 5-6 small holes in the pastry to allow steam to escape.
11. Bake in the oven for 35-40 minutes or until the pastry is golden brown.
12. Remove from the oven and let it rest for 3-4 minutes before turning out onto a plate.
13. Garnish with goat's cheese and serve.