On a lightly floured surface, fold over two cuts of 4”*6” puff pastry sheet (or flattened puff pastry dough) over on the long edge and make them 4”*3” pieces.
Roll the edge of your squares up to create a “frame” and press the edges evenly with a lightly-floured fork (helps the fork not to stick to and stretch the pastry sheets).
Slice the Brie into 1/8 inch pieces. If this takes a long time for you, refrigerate your pastry sheets while doing this. Lay Brie slices flat in the pastry shell. Sprinkle with ground nutmeg and salt.
Thinly slice the apple. I used 1/2 an apple for only one layer, but 2 layers of apple is also great. Mix apple slices with melted butter and maple syrup, and lay them on top of the Brie on pastry shell.
drizzle and brush the remaining of the maple syrup butter mixture onto the pastry shell.
Move the pastry shell to a parchment paper or baking mat (I just used the same paper that the puff pastry was wrapped in). Bake in 375F for 20 min, brush with egg wash, then 400F for another 10-15 minutes until golden brown.