We like to use smaller, sweeter Maine blueberries in this recipe, but any in-season variety works in these mini pies.
Heat oven to 425 degrees. Combine blueberries, sugar, flour, and salt in a large bowl. Gently toss to coat blueberries. Set aside.
On a clean, floured work surface, roll out half the dough to a 1/8-inch-thick square. Using a sharp knife, cut the square into quarters, and carefully drape each quarter over a 5-inch pie tin.
Place 1 1/2 cups blueberry mixture in each pie tin, mounding the berries in the center. Dot each pie with 1 1/2 teaspoons butter.
Again, on a clean, floured work surface, roll out remaining dough into a 1/8-inch-thick square. Using a sharp knife, cut square into quarters. Using a 1-inch round biscuit cutter, cut a hole from the center of each quarter. Carefully drape each quarter over blueberries so the steam hole is centered. Press edges together to seal. Trim edges around pie plates to form a 1/2-inch lip. Briefly refrigerate pies to chill the dough.
Dampen the 1/2-inch lip of dough with water. Using scissors, snip inwards from the outside edge of the pie at 3/4-inch intervals, making each cut about 3/4 inch deep. As you cut the dough, carefully fold in alternating tabs to create the bear-tooth crimping design. Return to refrigerator until chilled, about 30 minutes.
Transfer the pies to a baking sheet that is large enough for the tins not to touch. Brush each pie lightly with cold water; sprinkle with sugar. Transfer to oven, and bake until crust is golden brown, about 20 minutes. Reduce heat to 375 degrees, and continue baking until blueberry juice begins to bubble up, about 15 minutes more. Remove from oven, cool slightly, and serve with vanilla ice cream.
To serve a crowd, don't double or triple the pate brisee recipe; make as many single batches as needed. This recipe also will make one twelve-inch pie.