PIE DOUGH

1. Place flour, buckwheat flour, sugar and salt into a large bowl. Cut butter into chunks, and add to the flour. Toss lightly to coat. Working quickly, using a pastry blender or  your fingers,  cut the butter into the flour mixture until there are only pea-sized chunks left. You want a few lumps of butter remaining to keep the pastry nice and tender.
2. Combine ice, water and cider vinegar in a bowl. Sprinkle a few tablespoons of the ice water into the flour and butter mixture, and using a stiff spatula or your hands, mix in well. Continue adding water a tablespoon at a time ( I normally need about 8-10 tbsp) until you have a dough that holds together well, but is not too wet. Squeeze together with your fingertips to make a homogenous dough. Shape into two discs and wrap in plastic wrap. Rest in the fridge for at least two hours, or preferably overnight. 

FILLING AND BAKING

1. On a lightly floured surface, roll out one of the discs of dough to slightly larger than your 9" pie dish. Line the dish with the dough, leaving an overhang. Rest in the fridge until ready to fill.
2. In a large bowl, combine all of the filling ingredients. Toss well to combine using a spatula. Pour into the prepared dough-lined pie dish. 
3. Divide the second disc of dough into ⅔ of ⅓ of the disc. Roll out the ⅔ portion into a rectangle. Using a pastry wheel or multi-wheel cutter (which are the best ever), cut strips approx ¾ inch wide, or your desired lattice width. Place the strips over the filling, leaving a small gap between. Roll out the second portion of dough, and cut out stars using cutters. Arrange as desired on the pie. Trim the edges of the pie so that they are flush with the pie dish. Alternatively, decorate with your favourite lattice pattern.
4. Rest the pie in the fridge for at least 30 minutes. 
5. While the pie is resting, preheat the oven to 425˚f / 220˚c. Once the pie has rested, remove from the oven. Brush with egg wash (egg and water whisked together), and sprinkle liberally with raw sugar. 
6. Place the pie on a baking tray, and place in the oven. Cook for 20 minutes until the dough has set and is beginning to go golden. Reduce the oven temperature to 375˚f / 190˚c, and cook for a further 35-45 minutes, until the pastry is golden brown and the juices are bubbling. 
7. Remove from the oven and cool on a rack. Eat warm or at room temperature.