Prepare Puff Pastry: Roll out the puff pastry sheet on a lightly floured surface. Cut the pastry into small squares, about 2 inches each.
Assemble Bites: Place a piece of brie cheese in the center of each pastry square. Top with a small spoonful of cranberry sauce.
Fold and Seal: Fold the corners of the pastry square up around the cheese and cranberry, pinching the edges together to seal.
Brush with Egg Wash: Brush the tops of each pastry with the beaten egg to give them a golden finish.
Bake: Place the assembled bites on a baking sheet lined with parchment paper. Bake for 15-20 minutes, or until the puff pastry is golden brown and the cheese is melted.