1 sheet puff pastry,thawed
All-purpose flour, for rolling
1 round brie cheese (8 to 12 ounces, 5- to 7-inch diameter)
1 large egg, beaten
2 T preserves
Baguette slices or crackers, to serve
Baking sheet or pie plate
Warm the oven to 400°F: Place an oven rack in the middle position. Line a baking sheet with parchment and set aside, or bake your brie in a pie plate.
Dust your counter with a small amount of flour. Unwrap your puff pastry and place it on the counter. Rub your rolling pin with a little flour and roll the puff pastry until it measures roughly 11 inches by 11 inches. No need to get out a ruler; it's fine to estimate.
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.
Brush the pastry with the beaten egg. Be sure to get the sides and around the folds.
Bake the brie until the pastry is deep golden-brown, 35 to 40 minutes.
Allow to cool 5 to 10 minutes: This gives the hot cheese time to firm up a little.
Transfer to serving platter and serve warm.