Puff Pastry Pies with Brie and Caramelized Walnuts

1. Prepare the caramelized walnuts: Melt the butter in a pan over medium heat. Add the chopped walnuts and toast for about 2-3 minutes until lightly golden brown. Then add the sugar and stir until it melts and the walnuts are evenly coated. Continue cooking until the mixture is lightly caramelized. Remove from heat and let cool.
2. Fill the puff pastry parcels: Roll out the puff pastry on a lightly floured surface and cut into squares approximately 10x10cm. Place a slice of Brie in the center of each square and add a spoonful of the caramelized walnuts. Season with salt and pepper. Moisten the edges of the pastry squares and fold the pockets together. Press the edges firmly to seal.
3. Bake: Preheat the oven to 200°C (top/bottom heat). Place the puff pastry pockets on a baking sheet lined with parchment paper and brush with the beaten egg yolk. Bake in the preheated oven for 15-20 minutes, until golden brown and crispy.