Place one puff pastry square in each portion cup of the muffin pan, and gently push down the center.
Add a cube of brie to each cup.
Spoon approx. 1 tbsp cranberry sauce over each piece of brie.
Top with a pinch of the fresh rosemary and optional chopped nuts.
Sprinkle with finishing salt to taste.
Bake in oven according to puff pastry package instructions (about 15 min).
Remove from pan and serve immediately.