How to Make It
In a medium bowl, combine the flour and salt. Using your fingertips, rub the butter into the flour until it resembles coarse meal. Make a well in the center, pour in the beaten yolk mixture and stir until just moistened. Gather the dough into a ball. Working quickly, roll out the dough on a lightly floured surface into a 12-by-6-inch rectangle. Starting at a short end, fold the dough in thirds, forming a 4-by-6-inch rectangle. Wrap the rectangle in plastic and refrigerate overnight. Remove the pastry from the refrigerator 15 minutes before rolling out to soften slightly.
Halve the pastry. On a lightly floured surface, roll out 1 piece into a 12-inch round. Place the dough in a 9-inch pie plate without stretching. Do not trim the overhanging pastry. Roll out the second piece of pastry into a 10-inch round; transfer to a parchment-lined baking sheet. Refrigerate the pastry for 10 minutes.
Preheat the oven to 400°. In a small skillet, cook the bacon over moderately high heat until softened and just beginning to brown, about 2 minutes. Transfer the bacon to paper towels to drain.
Peel the potatoes and slice them 1/8 inch thick. Rinse the slices in cold water, drain and pat dry. In a medium bowl, toss the potatoes with the parsley; season with salt and pepper.
Arrange half of the potato slices in an even layer in the bottom of the prepared pie shell. Sprinkle the pieces of bacon on top and cover with the sliced eggs. Spread the crème fraîche over the eggs and top with the remaining potato slices.
Brush the overhanging edge of pastry with some of the egg wash. Place the top crust over the filling. Trim the pastry so it's even all around, then crimp the edges together to seal. Pierce the top crust to make 3 or 4 small vents. Brush the pie with some of the egg wash.
Bake the pie in the middle of the oven for 20 minutes. Lower the temperature to 350° and bake the pie for 1 hour, covering the edges with foil when brown. Lower the temperature to 300°, remove the foil and bake for 10 minutes longer. Let the pie rest for 10 minutes before serving.