Blueberry Turnovers with Lemon Glaze

1. Preheat oven to 400 degrees F. Line two baking sheets with parchment paper or Silpat liners and set aside. Allow puff pastry to thaw slightly on the counter while preparing the filling. 2. For the filling: In a small saucepan, stir together 1 cup blueberries, sugar, cornstarch, salt, and water. Stirring constantly, bring mixture to a boil over medium heat. Boil for 2 additional minutes, or until sauce thickens and becomes jammy. Remove from heat and stir in remaining blueberries, lemon juice, zest (if desired), and butter. Set aside to cool briefly. 3. On a lightly dusted work surface, unroll both sheets of partially thawed puff pastry and cut each sheet into quadrants to yield a total of 8 squares. 4. Into the center of each square, spoon a rounded tablespoon of blueberry filling. Brush egg wash along the edges of the pastry square and fold in half diagonally to create a triangle. 5. Using the tines of a fork dipped in water, press and crimp the edges of the pastry together to form a seal. 6. Brush the tops of the turnovers with egg wash and place on prepared baking sheets. 7. Bake until puffed and lightly golden, about 15 minutes. 8. While turnovers are in the oven, prepare the lemon glaze by whisking together powdered sugar, lemon juice, and zest (or extract) until smooth and no lumps remain. 9. Drizzle glaze over slightly cooled turnovers to serve.