Thaw puff pastry according to package instructions.
Preheat the oven to 350°F (176°C).
Cut brie cheese into 36 1-inch squares. Set aside.
Roll out the puff pastry to flatten the fold lines. Cut into 18 squares. A 4x6 grid should work with most pastry sheets.
Arrange the pastry pieces in a mini muffin tin and place a piece of brie inside the dough.
Add a spoonful of cranberry sauce over the brie. Sprinkle with bacon and pecans.
Bake at 350°F (177°C) for 15-20 minutes. (Keep an eye on them because the cranberry sauce can begin to caramelize, but I personally like the crunch. You want to remove them with the tops of the pastry is just browned.)
Let cool slightly, then garnish with small rosemary sprigs. Serve warm.
Notes
Buy pecans from the grocery store that are already chopped so that you don't have to chop them yourself! It'll save you some time and your future self will thank you.For the best flavor, make your own homemade cranberry sauce! The whole berries in the sauce add little pockets of tart flavor in each brie bites. But if not, feel free to buy canned cranberry sauce. Look for "whole berry" on the label — this is not the kind you slice. Prep your brie bites ahead of time and then bake them just before your party so that they are fresh and the melted brie is still warm.You can use crescent roll dough instead of puff pastry if you like.