PIE DOUGH

1. Place 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 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. 
3. On a lightly floured surface, roll one disc into a circle slightly larger than your pie dish. You want it to be approximately ⅛ inch (3mm) in thickness. Line the pie dish, leaving the extra dough overhanging. Trim the dough so there is about 1 inch overlapping the edge of your dish. Fold the dough back on itself, and crimp the border of the pie using two fingers of one hand and the thumb of the other. Roll out the second disc of dough, and cut out shapes using a cookie cutter or pie stamp. Place the shapes on a cookie sheet / baking tray. Refrigerate both the lined dish and the tray of stamps until ready to use. 

ASSEMBLY

1. Peel the apple, and then roughly grate. Place in a large bowl. Add the blueberries, lemon juice, sugar, brown sugar, flour, lavender essence, and culinary lavender. Mix well with a stiff spatula or your hands to combine, crushing some of the blueberries in the process. 
2. Pour the filling into the prepared pie dish. Arrange the stamped dough on the top of the fruit, making sure that there is a small amount of overlap. Rest the pie in the fridge for 15 minutes to set. 
3. While the pie is resting in the fridge, preheat the oven to 425˚f/ 220˚c. Place a baking tray on the bottom rack of the oven. 
4. Whisk together the egg and water in a small bowl. Brush the surface of the pie with the egg wash, and sprinkle liberally with turbinado / raw sugar. Take care not to get filling on the pastry. 
5. Place the pie on the baking tray in the oven. Bake for 20 minutes, or until the pastry has begun to go golden brown. Move the pie and baking tray to the middle of the oven, and decrease the temperature to 375˚f / 190˚c. Bake the pie for a further 35 to 40 minutes, or until the pastry is deeply golden and the filling is bubbling. 
6. Cool completely on a wire rack before serving.