In a large mixing bowl, beat the butter, cream cheese and flour on low speed until mixture forms a ball. Divide in half and wrap each portion in plastic wrap; refrigerate for 30 minutes.
On a lightly floured surface, roll out each portion into a 7-inch circle about 1/8 inch thick. Place one circle on an ungreased baking sheet. Place Brie on pastry and top with remaining pastry circle; pinch edges to seal. Flute bottom edge if desired.
In a small bowl, beat egg and water; brush over top and sides of pastry. Bake at 400° for 15-20 minutes or until golden brown. Immediately remove from the baking sheets. Let stand for 30 minutes before serving. Serve with crackers and fruit.