4 1/2 cups fresh blueberries
3/4 cup sugar
1/8 tsp kosher salt
5 1/2 tbsp tapioca flour
1 tbsp fresh orange juice
2 tsps orange zest
2 (9-inch) store-bought pie doughs
1 egg yolk whisked with 1 teaspoon water
Wash the berries and pat dry. Mash up half of the blueberries in a small bowl. In a medium bowl, whisk together the sugar, salt and tapioca flour. Add the mashed blueberries, orange juice and orange zest and stir to combine. Let the mixture sit for 15 minutes. Fold in the whole berries.
Line a 9-inch pie plate with aluminum foil. Place the blueberry mixture into the foil and place in the freezer until solid, about 6 hours.
Preheat the oven to 325 degrees F.
Unroll first piece of dough and place into a 9-inch pie pan, making sure the dough reaches to the lip of the pie pan. Trim excess, if necessary. Prick the bottom and sides with a fork and set aside. Unroll second piece of dough and cut into 1 1/8-inch wide strips that are at least 10-inches long.
Remove the frozen pie filling from the freezer and place into the prepared dough in the pan. Lightly brush the edge of the crust with the egg yolk. Lay 4 strips of dough across the top of the filling horizontally, leaving an even amount of space in between each strip. Fold back 2 alternating strips and lay down another strip in the middle of the pie, perpendicular to the other strips. As shown in the photo. Once you have a lattice, brush all the strips of dough with the egg yolk, trim excess dough and pinch strips and edge of crust in order to seal. Place on the bottom rack of the oven and bake for about 1 hour 15 minutes. The pie should be bubbling lightly around the edges. If the lattice is not browned enough in the center, place under the broiler for 1 to 2 minutes.
Let the pie cool down before serving.