Divide the dough into 8 equal portions, letting the dough stand at cool room temperature for 5-10 minutes to soften slightly. On a floured work surface, or between two floured pieces of parchment paper, roll each portion of dough into an approximately 5-inch round, about ¼-inch thick, turning the dough and dusting with flour to prevent sticking. Use a pizza wheel or a biscuit cutter to get an even circle.
Divide the blueberry filling amongst the pie rounds, mounding the fruit toward the center. Fold the dough over itself to make a half-moon shape and press down the edges. If the dough cracks, use your fingers to squish it back together.
Arrange the pies on a rimmed baking sheet lined with parchment paper and chill in the refrigerator until firm, about 20 minutes.
Position a rack in the upper third of the oven, and preheat to 400°F.
Remove the pies from the refrigerator. Brush the dough with milk, and sprinkle it with sugar. Use a paring knife to cut a few slits in the top of each pie to allow the steam to escape.
Bake the pies until the dough is golden, and the fruit is bubbling, 22-30 minutes. Remove from the oven, and while hot, use a thin, metal spatula to remove the pies from their parchment and onto a cooling rack (otherwise, caramelizing juices will cause them to stick). Let cool slightly, then enjoy warm, or at room temperature.
The hand pies are best enjoyed the day of baking when the crust is crisp, but they will keep for 2 days in an airtight container at room temperature.