Line a baking sheet with parchment paper or Silpat and set aside.
In a food processor, pulse together the flour and salt. Add the cubed butter (reserving 1 Tbsp) and pulse until the mixture forms pea-sized pieces. Slowly add 4 to 5 Tbsp of ice water in a steady stream and pulse until the dough starts to come together. It should be sandy and moist, but not wet. You may not need all of the water. Turn the dough out onto a lightly floured surface and work with your hands until it can be formed into a ball. Flatten into a disk with the heel of your hand. Cover tightly with plastic wrap and refrigerate for at least 1 hour.
In a small bowl, mix sugar, cinnamon, and ground ginger. Finely dice the crystallized ginger and set it aside. Slice pears in half lengthwise and core. Cut each half into ¹⁄₁₆-inch (1.5 mm) thick slices. Slice all the way through, but keep the pear halves together.
On a lightly floured surface, roll the dough into a 12-inch to 13-inch round ⅛-inch thick. Transfer the dough to the prepared baking sheet. Evenly sprinkle all of the sugar-spice mix and the crystallized ginger over the galette dough.
Arrange the pear halves on top, separating the slices like a fan, leaving a 1-inch (5 cm) border around the edge. Zest half a lemon and squeeze the juice over the pears. Roll the edge of the crust to the pears (adjusting the position of the pears if necessary) like a pie crust.
Beat the egg yolk and heavy cream in a small bowl, then brush over the crust. Sprinkle coarse sugar on top of the egg wash. Dot with an additional 1 Tbsp cubed unsalted butter if desired. Freeze the galette for at least 30-minutes (or cover and freeze overnight).
Preheat the oven to 425°F and position a rack in the middle of the oven. Bake the frozen galette for 15 minutes before reducing to 375°F and bake for another 45-50 minutes. Once the galette is browned, remove and sprinkle with chopped pistachios.