Let puff pastry thaw on the counter (the idea is to keep the dough chilled, but not get to room temp for optimal baking).
Using a rolling pin, stretch the dough into a 12in X 12in square. Place the Brie in the center of the puff pastry.
Using your jam of choice, evenly spread across the top of the cheese. Sprinkle half the thyme on top of the jam.
Fold the corners of the puff pastry over the brie in the center and press to create a seal.
Transfer to a lined baking sheet and cook for 30 minutes.
While cooking, beat one egg for an egg wash and add in the remaining thyme. At 30 minutes, take the puff pastry out and brush the egg over the top. Return to the oven and cook for an additional 15 minutes or until the pastry is golden brown.