Pre-heat your oven to 180ÂșC and line up baking tray with greaseproof paper.
Wash your blueberries and pat them dry. Add corn flour, icing sugar and mix until well combined and all blueberries are covered.
Roll out your pastry sheet and scoop on the prepared blueberries. Make sure you keep small border away from the edge. Fold the remaining pastry over the blueberries on the sides to keep your filling from spilling.
Egg wash the sides of the pastry and sprinkle with granulated sugar. Bake in the oven for 20-25 mins.