Stir and bring to a low simmer and cook, stirring frequently, until reduced and thickened and most of the cranberries have popped, about 10 minutes.
Remove from heat and let sit at room temperature while you move on to the next steps.
Prepare the puff pastry bites
Preheat the oven to 375 F .
Spray a mini muffin pan with cooking spray.
Unwrap the prepared puff pastry sheet and unfold. It is usually folded in thirds, so cut along the fold lines to make three strips. Then cut each strip so you have 4 pieces. You will have 24 pieces of puff pastry.
2 sheets puff pastry
Press the puff pastry squares in the prepared muffin wells, ensuring it is all the way on the bottom and sides of each well.
Cut the wheel of brie cheese into 24 equal pieces and press each piece in the bottom of each muffin well. You might have to fold/cut the wedges to press them in all the way.
8 ounces brie cheese
Top each piece of cheese with a spoonful of the prepared cranberry sauce over top. You will have leftovers.
1/2 cup cranberry sauce
Sprinkle the chopped walnuts and rosemary on top.
1/4 cup roughly chopped walnuts, 3 sprigs fresh rosemary
Bake for 15-18 minutes, until the puff pastry is puffed and golden and the cheese is melty.
Allow to cool for a few minutes before eating.
Notes
Leftovers can be stored in an airtight container in the fridge for up to 3 days. To reheat, microwave for a few seconds or pop in the air fryer until warm.