Preheat your oven to 375°F (190°C) and lightly grease a 12-cup standard muffin tin with cooking spray.

Unroll the thawed puff pastry sheet on a lightly floured surface and cut it evenly into 12 equal squares.

Press each puff pastry square gently into the cups of the prepared muffin tin, creating little tartlet shells.

Place a cube of brie cheese into the center of each puff pastry cup.

Spoon a teaspoon of whole berry cranberry sauce directly on top of the brie cheese in each cup.

Sprinkle the chopped pecans and fresh rosemary evenly over the cranberry sauce.

Bake in the preheated oven for 15 minutes, or until the puff pastry edges are golden brown and the cheese is fully melted and bubbly.

Allow the bites to cool in the pan for 5 minutes before carefully removing them. Serve warm.