Instructions

1. Preheat the oven to 400°F (200°C).
2. Slice the eggplant into rounds, about 1/4 inch thick, and arrange them on a baking sheet. Drizzle with olive oil, and season generously with salt and black pepper.
3. Roast the eggplant in the preheated oven for 15-20 minutes, or until tender and slightly golden, turning them halfway through for even cooking.
4. While the eggplant is roasting, roll out the thawed puff pastry on a lightly floured surface to fit a 9-inch tart pan. Carefully transfer the pastry to the tart pan, pressing it gently into the bottom and up the sides.
5. Prick the bottom of the pastry with a fork to prevent it from puffing up during baking.
6. Once the eggplant is roasted, layer the slices evenly over the pastry.
7. Sprinkle the grated Gruyere cheese and the chopped thyme over the roasted eggplant, ensuring an even distribution.
8. Brush the edges of the pastry with the beaten egg for a golden finish.
9. Bake the tart in the preheated oven for 25-30 minutes, or until the pastry is golden brown and the cheese is melted and bubbly.
10. Allow the tart to cool slightly before slicing and serving. Enjoy warm or at room temperature.