Preheat oven to 350° F.
On a lightly floured surface, roll out the puff pastry to approximately 11 inches square.
Spread the pumpkin butter evenly in the center of the pastry to form a 4 inch circle. Sprinkle the walnuts evenly over the pumpkin butter and top with the brie.
Fold the corners of the pastry up over the brie and pinch to seal.
Place the pastry wrapped brie on a baking sheet lined with parchment and brush the surface with the egg.
Bake for 25-30 minutes or until the pastry is puffed and golden brown.
Remove from the oven and allow to rest for 5 minutes.
Serve warm or at room temperature.