Instructions:

1. Preheat the oven to 400°F (200°C).:

2. Heat olive oil in a pan over medium heat. Add onion and garlic, cooking until softened.:

3. Add the mushrooms and thyme, cooking until mushrooms are tender and any liquid has evaporated. Season with salt and pepper.:

4. Roll out the puff pastry on a floured surface and place it on a baking sheet lined with parchment paper.:

5. Spread the mushroom mixture over the pastry, leaving a 1-inch border around the edges.:

6. Sprinkle goat cheese over the mushrooms.:

7. Fold the edges of the pastry over the filling, brushing the edges with the beaten egg.:

8. Bake for 20-25 minutes until the pastry is golden brown.:

9. Garnish with fresh parsley before serving.