Thaw the puff pastry according to the package directions.
Preheat your oven to 400°F (204°C). Spray a mini muffin pan with nonstick cooking spray.
Place the brie cheese in the freezer for 20 minutes or until firm to the touch.
On a well-floured surface, roll the puff pastry into a rectangle. Cut into squares about 2 x 2 inches.
Press the pastry squares into each well of the muffin pan, letting the excess stick up over the edges.
Place a piece of brie into the center of each pastry square.
Top each with about 1 tsp of cranberry sauce.
Bake for 15 minutes or until golden brown and the cheese is bubbly.
Let cool in the pan for 5 minutes, then remove. Sprinkle with chopped pistachios.