Preheat your oven to 375°F (190°C). Lightly grease a 24-slot mini muffin tin with non-stick cooking spray to ensure the pastry bites release easily after baking.
On a lightly floured surface, roll out the thawed puff pastry sheet into a large rectangle. Use a pizza cutter or a sharp knife to cut the dough into 24 equal-sized squares (roughly 3×3 inches each).
Gently press each pastry square into the slots of the prepared mini muffin tin. The corners should hang slightly over the edges, creating a rustic, flowery look.
Cut the Brie cheese into 24 small cubes (about 1 inch each). Place one cube of cheese into the center of each pastry-lined muffin slot. You can leave the rind on the Brie as it is completely edible and helps the cheese hold its shape.
Spoon about one teaspoon of cranberry sauce on top of each piece of cheese. Sprinkle a few chopped pecans or walnuts over the sauce for an added crunch.
Place the muffin tin in the oven and bake for 12 to 15 minutes. The bites are done when the pastry is puffed and golden brown and the cheese has melted beautifully.
Remove the tin from the oven and let the bites cool for 5 minutes. While still warm, garnish each bite with a tiny sprig of fresh rosemary and an optional drizzle of honey.