Preheat your oven to 190C or 170C if fan assisted.
To make the pastry, add the sugar, flour and butter to a bowl. Use your finger tips to make it into a breadcrumb consistency and make sure all the butter is thoroughly mixed in. Now add the water and mix until the pastry forms a ball of dough. Cling film and leave in the fridge for at least half an hour.
On a floured surface, roll out two-thirds of the pastry and line your pie dish with it. Allow some overhang as the pastry shrinks in the oven. Make some holes in the base with a fork and add baking beans before blind baking in the preheated oven for 15 minutes.
Wash, peel, core and cut up your apples. Place these and the berries with sugar to taste in the baked pastry. Add the cinnamon.
Roll the remaining pastry and trimmings together into a square and cut out 8 strips of pastry that should be long enough to cover both ends of your pie. Weave the strips of pastry evenly over the fruit to create a lattice pattern and push them into the edge of the tart. Trim the overhang of pastry, and use a fork to press down the edges. Brush the top of the lattice with the egg and milk and scatter on a bit of sugar.
Bake for around 50 minutes to an hour until lovely and juicy.
