In a large mixing bowl, add flours, sugar and salt and stir to combine. Cut cold butter into the flour using a pastry cutter, two knives, or a food processor, until the mixture resembles coarse meal.
If using a food processor, add cold water while machine is running, until the dough holds together (about 15-30 seconds). Otherwise, add water to the bowl and using a fork or your hands, mix together until dough forms.
Turn the dough out onto a sheet of plastic wrap. Press into a flat, round disc, wrap tightly, and refrigerate for 30-60 minutes.
Meanwhile, prepare the fruit. In a medium mixing bowl, toss pears with lemon juice after slicing to avoid browning. Add cornstarch, ginger, cinnamon, and maple syrup and mix until evenly coated.
Preheat oven to 400 degrees F and line a baking sheet with parchment paper.
Roll out dough onto a lightly floured surface, about 12 inches in diameter, 1/8 inch thick. Transfer dough to parchment paper. Arrange pears in a spoke pattern on the dough, leaving a 4-inch border all around.
Add wild blueberries to the mixing bowl with cornstarch mixture and stir to coat with the remaining mixture. Distribute wild blueberries evenly on top of pears.
Fold the border of dough over the fruit, pressing gently to adhere the folds.
Thin out the beaten egg with a splash of water and brush egg mixture over the dough edges and sprinkle edges with sugar.
Bake at 400 degrees F for 45-60 minutes, or until crust is golden brown and fruit is tender.
Transfer the galette with parchment paper onto a cooling rack. Gently pull parchment paper out from underneath while keeping the galette on the cooling rack. Let cool briefly before serving warm or at room temperature.
Whipped cream for serving is optional.
If you don’t have whole-wheat pastry flour, use whole-wheat flour instead. Or, you can simply omit whole-wheat flour and use 2 cups all-purpose flour.
You can substitute any type of sugar for dusting.
Take advantage that galettes can be made ahead of time and will keep in the refrigerator for up to three days. Or, you can make the dough ahead of time and freeze it until ready to use!