2) Add the water, 1 tablespoon at a time, pulsing briefly after each spoonful of water. Keep adding water until the dough just begins to gather into larger clumps.
3) Transfer equal amounts of the dough into 2 resealable plastic bags and pat each into a disk. Leave to rest in the refrigerator for at least 30 minutes.
4) Remove 1 of the disks from the bag to a flour coated surface. Using a rolling pin, roll the dough out to a 25cm round. Gently fit the rolled dough into a 22.5cm pie pan, and refrigerate while you prepare the torte ingredients.
For the filling:
1) Preheat the oven to 190C/Gas 5. Cook the bacon in a frying pan over a medium heat until just crispy. Drain on a paper towel lined plate and set aside. Crumble the bacon when cool to the touch.
2) Meanwhile, in a small saucepan, heat the thyme and cream over a low heat to a bare simmer. Turn off the heat and leave to steep for about 5 minutes. Remove the thyme sprigs.
3) Remove the pie pan from the refrigerator. Cut the potatoes in half lengthwise and then finely into slices. Working in circles, arrange the potato slices in the pastry case, stopping to season each layer with salt, pepper and about 1/4 of the crumbled bacon. Continue layering until the pie pan is nearly full.
4) Top with an even layer of the cheese and gently pour the cream around and over the entire pie, allowing it to seep down between the potato slices. (You may not use all the cream.)
5) Roll out the remaining disk of refrigerated pastry. Cover the pie with the dough and crimp the edges closed. Brush the top and edges of the crust with egg wash. Make a few slits in the centre of the top crust, for the steam to escape, and put the pie pan on a baking sheet.
6) Bake the torte until the crust is browned and crispy and the potatoes are cooked through, about 60 to 70 minutes. If the crust edges get too brown, cover them with strips of aluminium foil. Remove the pie from the oven and allow to rest for at least 15 minutes before cutting into wedges and serving.