Steps:

• Heat the oven to 400°F. Arrange a rack in the middle of the oven and heat the oven to 400°F. Line a baking sheet with parchment and set aside, or bake your brie in a pie plate.
• Roll out the puff pastry. Dust a work surface with a small amount of flour. Unwrap the puff pastry and place it on the flour. Coat a rolling pin with a little flour and roll out the puff pastry into a rough 11-inch square. No need to get out a ruler; it's fine to estimate.
• Wrap the brie in the pastry. Place the round of brie in the middle of the pastry. Top with any optional extra toppings, if using. Fold the corners over the brie, forming a neat package. Use your hand to gently press the edges against the brie and neaten up the sides.
• Transfer the wrapped brie to the baking sheet or pie plate. Place the wrapped brie to the baking sheet or pie plate. If the pastry has warmed and is no longer cool to the touch at this point, place refrigerate for 10 minutes, or until you're ready to bake and serve.
• Brush with egg. Brush the pastry all over with the beaten egg. Be sure to get the sides and around the folds. Try not to let the egg puddle under the brie.
• Bake until golden-brown, 35 to 40 minutes. Bake until the pastry is deep golden-brown, 35 to 40 minutes.
• Allow to cool 5 to 10 minutes. Set aside to cool for 5 to 10 minutes. This gives the hot cheese time to firm up a little. Cut into the brie early and most of it will gush right out — which is still delicious, but less tidy.
• Transfer to a serving platter. Use the parchment paper to transfer the brie to a serving plate. If you baked it in a pie plate, serve straight from the plate, but double check that the plate has cooled enough to handle.
• Serve warm. Arrange sliced baguette or crackers around the brie and serve while warm.