Gather all ingredients.

Use a sharp paring knife to score the side of Brie all the way around, cutting directly on the equator through the rind. Wrap string or dental floss around brie on the scored cut. Loop one end of the string over the other to make a half knot. Pull the ends of the string in opposite directions to cut Brie in half.

Lay Brie halves, cut-side up, on a flat work surface. Spread cranberries over one half and walnuts on the other, pressing down gently into cheese.

Quickly put the 2 sides back together with cranberries on top of walnuts. Press together and stuff back in any cranberries or walnuts that fell out.

Roll out puff pastry on a floured surface to about 1/8-inch thickness. Place Brie in the center of pastry. Gently pull up edges to ensure there is enough dough to entirely wrap Brie. Trim off the corners if there is too much dough.

Mix together egg and water in a small bowl. Brush egg wash over dough. Fold one edge of dough over Brie and then the opposite side. Fold over the remaining edges to completely encase Brie. Trim off excess dough as needed. Flip Brie over so the seam is at the bottom; gently press in the sides to snug dough against Brie. Brush the top and sides of wrapped Brie with egg wash.

Cut out decorative pieces from remaining puff pastry and place on Brie. Lightly brush decorative pieces with egg wash. Place Brie in the freezer for 1 hour.

Preheat the oven to 425 degrees F (220 degrees C). Line a rimmed baking sheet with parchment paper. Place Brie on the prepared baking sheet and bake on the center rack in the preheated oven until it is browned and leaking cheese, 20 to 25 minutes. (Only rarely does Brie not leak through.)

Serve and enjoy.