Pre-heat oven to 375F
Gently stir together peaches, berries, sugar and corn starch in a bowl. Let stand 5 min and stir again.
Unroll pastry onto baking sheet, leaving on parchment.
Spoon mixture into centre of pastry, leaving 2-inch border uncovered.
Brush edge with egg and fold over filling, overlapping and pleating as you go around. (Will be a circle and not all filling will be covered).
Brush top of pastry with some egg.
Sprinkle with sugar and bake for 20 min.
Rotate baking sheet and bake for another 20-25 min, until pastry is puffed and golden brown and filling is bubbly.
Allow to cool for 10 min before serving