INGREDIENTS
For the crust:

• 2 ½ cups all-purpose flour
• ¼ cornmeal (I only had coarse)
• 3 tablespoons sugar
• 2 grams salt (about 1/2 teaspoon)
• 12 tablespoons butter, unsalted, chilled, cut into small cubes
• ¼ cup vegetable shortening, chilled, cut into small pieces

For the filling:

• ¾ cup sugar
• ¼ cup cornstarch
• ⅛ teaspoon salt
• Pinch of cinnamon
• 3 tablespoons salted butter, cut into small pieces
• 6 cups fresh blueberries (about 3 pints)
• 2 tablespoons milk
• 1 tablespoon raw sugar

INSTRUCTIONS
Make the crust
Blend flour, cornmeal, sugar and salt in a food processor. Add butter and shortening, then pulse until mixture resembles coarse meal. Add 4 tablespoons ice water and blend until dough forms a ball, adding more ice water, a half-tablespoon at a time (up to 2 additional tablespoons), if dough is dry. Divide dough in half, flatten into two round disks, wrap in plastic and chill at least 1 hour.
make the filling: whisk together sugar, cornstarch, and salt. Fold in 4 cups blueberries, 2 tablespoon water. Let stand at room temperature about 45 minutes until juices form. Gently fold in the remaining 2 cups blueberries.
Assemble the pie
Heat oven to 400°. On a floured surface, roll out one dough round into a rectangle. Transfer rolled-out dough to a 9 x 13 inch quarter sheet pan and fill with blueberry mixture. Take the small pieces of butter and dot sprinkle over the blueberry mixture. Roll out the second dough round, then use it to cover the pie, decoratively crimping together dough edges to seal. Alternatively you can cut it into strips and make a lattice top. Brush with milk and sprinkle with raw sugar.
Place pie pan on a rimmed cookie sheet and bake for 25 minutes. Reduce oven temperature to 350° and continue baking until crust is golden brown and filling is bubbling, about 35 minutes more. Spoon any escaped juices onto pie. Transfer to a rack and cool completely before serving.