Line a baking sheet with parchment paper or Silpat and set aside.
In a food processor, pulse together flour and salt. Add cubed butter and pulse until mixture forms pea-sized pieces. Slowly add ice water in a steady stream and pulse until the dough starts to come together. It should be sandy and moist, but not wet. 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 the sugar, cinnamon, and ground ginger. Finely dice the crystallized ginger and set aside. Slice the 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 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 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.