First, prebake the pie crust. Position a rack in the center of the oven and preheat the oven to 350°F. Line a half sheet pan with parchment paper.
Prep the pie crust. Place the frozen crust, still in its plate, in the center of the pan. Cover the crust with foil, making sure the crimped edges are completely covered and that there are no gaps between the foil and the crust. Fill with pie weights and spread them out so they are more concentrated around the edges of the crust.
Prebake the crust. Bake for 30 minutes. While the crust is in the oven, make the egg wash: In a small bowl, whisk together the egg white and water.Remove the sheet pan from the oven, keeping the oven on. Carefully lift out the pie weights and foil. Use a pastry brush to coat the bottom and sides of the pie crust (but not the crimped border) with a thin layer of egg wash. Bake, uncovered, for an additional 5 minutes. Set aside on a wire rack to cool completely. Once the crust is cool, make the ganache layer. Place the dark chocolate in a small heatproof bowl. Bring the heavy cream just to a heavy boil over medium heat in a small, heavy-bottomed saucepan. Remove from heat and immediately pour over the chocolate, then place a heatproof plate over the bowl to create a makeshift lid. Let sit, undisturbed, for 5 minutes.Remove the plate. Whisk slowly but steadily until the ganache is thick, smooth, and shiny. Scrape the ganache into the cooled pie shell and spread evenly over its bottom and sides with an offset spatula. Place the shell in the freezer to set the ganache while making the filling. Prep your oven. Position a rack in the center of the oven and preheat the oven to 375°F. Line a half sheet pan with parchment paper.
Make the pecan filling. In a large bowl, mix together the brown sugar, flour, and salt. Mix in the milk until combined. Mix in the eggs, one by one, adding the next egg only when the previous egg has been incorporated. Mix in the vinegar, vanilla, butter, and diced pecans.Place the ganache-coated pie crust on a parchment-lined half sheet pan and pour in the filling. Scatter the pecan halves on top. Bake the pie. Bake for 50 to 55 minutes, or until the edges are set and the center of the pie just slightly jiggles. Cool on a wire rack.
Serve and store. Serve slightly warm or at room temperature. The pie can be kept at room temperature, under a cake dome or a large bowl turned upside down, for 1 day. After that, cover tightly in plastic wrap and refrigerate for 2 more days.