Preheat and Prepare: First things first, preheat your oven to 200°C (180°C fan/Gas Mark 6). Line a large baking tray with parchment paper. This will prevent any sticking and make cleanup much easier.

Prepare the Pastry: Carefully unroll your sheet of puff pastry onto the prepared baking tray. Using a small, sharp knife, lightly score a 1.5cm border all the way around the edge of the pastry. Be careful not to cut all the way through.

Dock the Centre: Using a fork, prick the pastry inside the border all over. What works best for me is to be quite thorough with this step. This 'docking' process prevents the centre from puffing up as much as the edges, creating a stable base for your toppings, much like a traditional pizza crust. You can learn more about the science behind working with puff pastry to get the best results.

Egg Wash the Border: Brush the beaten egg over the 1.5cm border you scored. This will give the edges a beautiful, deep golden-brown shine once baked.

Add the Toppings: Spread the cranberry sauce evenly over the centre of the pastry, right up to the scored border. Arrange the slices of brie on top of the sauce. Sprinkle over the chopped rosemary and thyme leaves.

Final Touches: Drizzle the olive oil over the toppings and finish with a good pinch of sea salt flakes and a few grinds of black pepper.

Bake to Perfection: Place the tray in the preheated oven and bake for 20-25 minutes. You're looking for the pastry border to be deeply golden and well-puffed, and the brie should be completely melted and bubbling.

Rest and Serve: Remove from the oven and let it cool on the tray for about 5 minutes. This allows the cheese to set slightly, making it easier to slice. Using a pizza wheel or a sharp knife, cut into 12 even squares. Serve warm.