Preheat oven to 375°F (190°C).
Cut puff pastry sheet into 12 equal squares.
Place each square into a mini muffin tin, pressing gently to form a cup.
Cut brie into small cubes and place one cube inside each pastry cup.
Top with a spoonful of cranberry sauce.
Brush edges of pastry with beaten egg.
Bake 12 to 15 minutes, until golden and bubbly.
Optional: garnish with a small rosemary sprig before serving.