In a food processor, pulse together the flour and the salt. Add the butter. Pulse until mostly crumbly, with some large pieces. With machine running, add 4 tablespoons of the water. Process until dough just holds together. If it is too dry, add remaining water, as needed. Dough should not be wet. Turn dough out onto plastic wrap. Divide in half. Press each half together into a disk, wrap in plastic wrap, and refrigerate one hour, or overnight.
On a lightly floured surface, roll out one disk of the dough to a 12-inch circle. Brush off excess flour. Fit dough into a 9-inch pie dish. Press the edges down around the inside. Trim dough to a half inch over the dish. Roll our remaining disk of dough. Transfer disk to parchment-lined baking sheet. Chill pie shellnand disk of dough. If desired, rolln the remaining dough scrapes into a thin disk. Cut out shapes with a small leaf cutter. Chill the leaves on the baking sheet with the disk of dough.
In a large bowl combine the pecans, cinnamon, salt, sugar, cranberries, pears, butter, and tapioca. Toss well. Transfer the mixture to the cold pie shell.
Whisk the egg with 2 teaspoons of water. Brush the egg glaze around the rim of the dough. Transfer the cold disk of dough on top, press down gently. Press the top and bottom pieces of dough together, around the rim. Trim the top dough with scissors to about 1"-inch. Fold it under. Crimp the edge of the pie as desired.
Brush the surface and edges of the pie with the egg wash. Make 3 slits in the top for steam to escape. If using, apply the cold leaves to the top of the pie with the egg wash. Sprinkle sanding sugar over the top if desired. Freeze the pie for 30 minutes to firm up the butter. Heat the oven to 400, with a rack in the lower third.
Bake until the crust begins to brown, about 20 minutes. Reduce heat to 350. Continue to bake until crust is richly golden brown, rotating as needed, 40-55 minutes. Transfer pie to a wire cooling rack. Cut when cool. Pie may be kept at room temperature up to 2 days, lightly covered with plastic wrap.