Using a food processor or a pastry blender in a large bowl, stir the flour, salt and sugar together. Add the butter and cut into the flour mixture (or pulse briefly in the food processor) until mostly pea size pieces of butter remain. A few larger pieces are okay. If using a food processor, transfer the flour-butter mixture to a large bowl.

Combine the water, cider vinegar and ice in a bowl. Sprinkle 2 tablespoons of the ice water over the flour mixture, and mix and cut it in with the bench scraper, spatula or your fingers until fully incorporated. Continue to add the ice water mixture, 1-2 tablespoons at time, until the dough just comes together with a few dry bits. This normally takes about 10-12 tablespoons total.

Divide the dough in half and shape into two flat discs. wrap in plastic and refrigerate for at least 1 hour or up to 3 days.

Preheat the oven to 220°C.

Roll out one disc of dough to line a greased, 9 inch (22cm) pie pan: place the dough on a large piece of baking paper on your work surface with a sprinkle of flour (it may need to rest for 5 minutes to soften enough to roll). Use a rolling pin to roll out to about 30cm diameter. Move the dough onto the pie plate by folding the baking paper & dough in half over your rolling pin, peeling hte backing paper over and unrolling the dough onto your pie plate. Press firmly into the bottom and sides of the pan and trim the edges, leaving about 1cm overhang of the rim for crimping later. Place in the refrigerator.

Reflour your surface and roll the second disc out. Use a sharp knife or pizza cutter to cut 2-3cm strips of dough, long enough to cover the diameter of the pie tin. Refrigerate while you prepare the filling.

Combine the peaches, blackberries, caster sugar, vanilla, lemon zest and juice, and flour in a large bowl and toss to combine. Pour the filling into the refrigerated pie shell, making the fruit as even and flat as possible. Arrange the lattice on top, (see HERE for instructions) and crimp the edges.

Chill the pie in the freezer for 10-15 minutes to set the pastry.

Make the egg wash by whisking together 1 egg with a tablespoon of water.

Place pie on a baking tray to catch any overflow and brush the egg-wash over the lattice and crimped edge. Sprinkle liberally with demerara sugar.

Bake for 20-25 minutes or until the pastry is set and beginning to brown. Lower the oven temprature to 180°C, and continue to bake for another 20 minutes or until deep golden and bubbling.

Allow to cool completely on a wire rack, 2-3 hours. Serve with scoops of olive oil ice cream (recipe below)