Preheat the oven to 350°F and line a baking sheet with parchment paper.
Remove the chilled dough from the fridge and unwrap. On a lightly floured surface, roll the dough into a rough 12-inch circle, about 1/8-1/4 inch thick. A little irregularity is expected and makes for a beautiful galette.
Slice the pears and arrange them in the center of the dough disk, leaving a couple inches of dough uncovered on all sides. Sprinkle the cinnamon, nutmeg, and ginger over the pear slices.
Fold the sides of the dough up to cover the edges of the pear slices.
In a small bowl, whisk the egg, then brush it all over the exposed pastry dough. Sprinkle the brown sugar over the galette.
Optional: Chill the assembled galette for 15-20 minutes before baking for an extra flaky crust and minimal juice leakage.
Bake for 15-20 minutes, or until the top is golden brown, the filling is bubbly, and the bottom of the pastry is cooked through.
Remove from oven and let the galette rest on the baking sheet for 20-30 minutes for optimal presentation and texture.
Slice and serve warm.