Preheat oven to 425 degrees F.
On a lightly floured surface, unfold the puff pastry sheets and gently roll until 1/4-inch thick. If using puff pastry cups, skip to step X.
Using a 2½” round cutter, cut 9 circles on each pastry sheet and transfer to a baking sheet lined with parchment paper. Then, use a 1½” cutter to cut a hole in the center out of half the circles, creating rings. Place the rings on top of the whole circles. Discard the cut centers.
Place the raw vols au vent in the freezer for 15 minutes (and no more than 30 minutes).
When oven is preheated, brush the center of the vols au vent with the egg wash. Do not brush the edges, so the puff pastry can rise evenly.
Bake until golden brown, about 12-15 minutes.
Remove the pastries from the oven. If the centers puffed a lot, use a pairing knife to cut them out or push them in with your fingers, to created a hollow space for the cheese.
Insert the brie cubes inside the hollowed center. Top with the cranberry sauce and crushed pistachios.
Bake again until the cheese has melted, about 10 minutes.
Let them cool slightly and serve immediately!