PIE DOUGH

1. Place flour, salt, pepper, and parmesan 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 large 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.
3. Squeeze together with your fingertips to make a homogenous dough. Shape one into a disc and one into a rectangle, and wrap in plastic wrap. Rest in the fridge for at least two hours, or preferably overnight.  (See notes for rolling out dough during resting period)

MUSHROOM FILLING

1. Heat a glug of oil in a large frying pan or skillet over medium high heat. Add about a third of the mushrooms, and cook, stirring occasionally, until golden brown. Remove and transfer to a bowl. Season with salt and pepper. Repeat the process in two more batches with the remaining mushrooms until all are cooked.
2. Lower the heat to medium and add the butter. Add the onion and garlic, and cook, stirring frequently, until the onion is translucent. Add the flour and stir to incorporate, then add the stock, cream, and soy sauce, and cook over medium heat, stirring often, until the sauce has thickened.
3. Remove from the heat and add in the Filippo Berio Sundried Tomato Pesto and thyme. Add the cooked mushrooms and stir to incorporate and to ensure the mushrooms are covered in the sauce. The filling will seem thick. Taste and adjust for seasoning if needed.
4. Transfer to a container allow to cool to room temperature. This filling can be made up to a few days ahead and stored in an airtight container in the fridge.

ASSEMBLY

1. On a lightly floured surface, roll the disc into a circle slightly larger than your pie dish. You want it to be approximately 1/8 inch (3mm) in thickness. Line a 9" pie dish, leaving the extra dough overhanging. Trim the dough so there is about 1 inch overlapping the edge of your dish.
2. Place in the fridge while you prepare the lattice.
3. Roll out the second piece of dough (the rectangle) into a rough rectangle approximately 1/8 inch thick. Use a pastry cutter to cut strips for your lattice.
4. Add the cooled filling to the lined pie dish, spreading down slightly with a spoon or spatula. Lattice the top (I did a very simple pattern and laid the strips down), and either cut the lattice flush with the edge of the pie, or fold the edges over and crimp as desired.
5. Rest the pie in the fridge for at least 30 minutes. 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.
6. Brush the pie with egg wash. Bake at 425˚f / 220˚c for 20 minutes, or until the pastry is set and beginning to go golden. Reduce the temperature 375°f / 190°c, and bake until the pastry is deeply golden and the filling is bubbling, 40 to 50 minutes.
7. Remove from the oven and cool on a wire rack.
8. Store leftovers in an airtight container in the fridge, and re-warm in the oven before serving.