Perfect Blackberry Pie

Directions

1. 1
   Adjust oven rack to lowest position and place four 9-inch unglazed quarry tiles on rack to form an 18-inch square.
2. 2
   (A pizza stone will work, too.) Preheat oven to 400 degrees and let tiles heat for at least 30 minutes.
3. 3
   Puree 1 cup of the blackberries in a food processor fitted with the metal blade; set aside.
4. 4
   Stirring constantly with a rubber spatula, bring the sugar, salt, starch and blackberry puree to the consistency of thick jam over medium-low heat in a large saucepan.
5. 5
   Stir in lemon zest.
6. 6
   Pour thickener over remaining blackberries and stir to combine.
7. 7
   Pour blackberry filling into bottom pie shell and dot with the 1 Tb.
8. 8
   butter.
9. 9
   Cover with top layer of pastry dough.
10. 10
    Set an 18-inch square of heavy-duty foil on tiles or pizza stone.
11. 11
    Set pie on foil and bake for 20 minutes.
12. 12
    Remove pie from oven, brush with beaten egg white, sprinkle with 1 1/2 Tbs.
13. 13
    sugar.
14. 14
    Bake until golden brown, about 20 minutes longer.
15. 15
    Bring foil around pie to loosely cover.
16. 16
    Bake until filling bubbles, 15-20 minutes longer.
17. 17
    Cool on a wire rack, 2-3 hours.