Preheat oven to 400°.
Mix all the ingredients in a large bowl.
Place the pastry rounds on a lightly floured work surface.
Divide the blueberries between the pastry rounds, mounding the berries as best as possible in the center of each round (those blueberries tend to roll and scatter).
With each galette, gently fold edges of dough over the fruit mixture, pleating as you go, and leave an opening in the center.
Brush the pastry with the egg wash.
Sprinkle the pastry dough with a little bit of sugar.
Using a spatula or a cake lifter, transfer the galettes to a parchment-lined sheet pan.
Place galettes in the oven and bake at 400° F for 10 minutes, and then reduce the heat to 375° F.
Bake in 375°F oven until pastry is golden brown and fruit center is bubbling, about 30 to 35 minutes.
Remove galettes from oven and allow to cool for about 20 minutes, and then carefully, using a spatula to lift them, transfer to a wire rack to cool completely.
Garnish with a few fresh blueberries.
Serve with a scoop of vanilla ice cream, crème fraiche, or a dollop of whipped cream.