Perfect Blackberry Pie

• Ready In: 1 hr 40 mins
• Yields: 1 pie

Ingredients

•  classic  pie crust (see Classic Pie Crust, Idiot Proof Step-By-Step Photo Tutorial)
• 5 1⁄2 cups fresh blackberries
• 3⁄4 cup granulated sugar, plus
• 2  tablespoons granulated sugar
• 1  pinch salt
• 1⁄4 cup potato starch or 1⁄4 cup potato flour
• 1  teaspoon  finely grated lemon, zest of
• 1  tablespoon butter, cut into small pieces
• 1  egg white, beaten,for pastry wash
• 1 1⁄2 tablespoons granulated sugar

Directions

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