Preheat oven to 350°F (180°C). In a large bowl, combine peaches, ½ cup (4oz/115g) sugar and salt together and let sit for 30 minutes.

After 30 minutes, strain the accumulated peach juice over a saucepan over medium heat (returning peaches to the bowl) and let boil until reduced and thickened to a syrup.

Sprinkle peach syrup, the remaining 1/2 cup (4oz/115g) sugar, flour, cornstarch, lemon and vanilla over the peaches and toss to coat evenly.

Roll out one pie crust and line a 9-inch pie pan with it.

Pour the peach filling into the pie crust and dot with the butter.

Roll out the second pie crust and cut into small squares. Lay the squares with overlapping corners in rows on top of the pie making sure there is plenty of open space for the juices to evaporate.

Brush egg wash all over the top crust. Sprinkle with coarse sugar.

Bake the pie for about 1 hour and 15 minutes, or until the crust is golden brown and the juices are bubbling. Let cool for 4 hours before cutting and serving with vanillla ice-cream. Store the pie loosely covered, at room temperature for up to 2 days.