In a medium-sized saucepan, combine 1 1/2 cups blueberries, 1/4 cup sugar and the lemon juice.  Cook over medium heat for about 5 minutes, stirring occasionally.  Reduce heat to medium-low and cook 3 minutes, until all berries have burst.

Meanwhile, in a small bowl, stir the cornstarch and 2 tablespoons of water until smooth.  Add the cornstarch slurry to the berries and cook for just 1 minute, until thickened.  Remove from heat and stir in the remaining 1/2 cup of blueberries.

Place saucepan in a bowl of ice water.  Stir mixture frequently, until cooled.

Preheat oven to 375°F.

Unroll 1 pie crust on a lightly floured work surface, then roll out to 1/16-inch thickness.  Using a 4 1/2-inch round cutter, cut out 4 rounds.

Place 2 tablespoons of the blueberry filling on half of each round, leaving a 1/2-inch border.  Dampen the edges with a fingertip dipped into water.  Fold dough over filling, pressing the edges to seal.  Crimp with the tines of a fork that has been dipped in flour.  Refrigerate for 15 minutes. Repeat with remaining piecrust and filling.

Brush pies with the egg wash and make 2 slits in the center of each (for steam to escape). Sprinkle evenly with 1 tablespoon of sugar.  Bake for 20 minutes, until golden.  Let cool. 

If desired, serve with a side of whipped cream or a scoop of vanilla ice cream.