2) 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.
3) Line a 22.5-cm pie plate with aluminum foil. Place the blueberry mixture into the foil and place in the freezer until solid, approximately 6 to 8 hours.
4) Once the filling is frozen, remove from the aluminum foil and wrap in plastic wrap and store in a freezer bag for up to 3 months.
5) Preheat the oven to 162 degrees C.
6) Unroll first piece of dough and place into a 22.5-cm 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 5-cm wide strips that are at least 25-cm long. 7) Using a ruler that is 5-cm wide, lay the ruler on the dough at 1 edge and roll across dough using the edge of the ruler as you go to cut through the dough.
8) 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.
9) Fold back 2 alternating strips and lay down another strip in the middle of the pie, perpendicular to the other strips. Return the strips that are laid back to their original position.
10) Next, fold back the other 2 strips and lay down a strip to the left of the center perpendicular strip. Return the strips that are laid back to their original position and repeat on the other side of the perpendicular strip, folding back the same 2 strips as you did on the other side.
11) 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.
12) 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.
Place the pie on a rack and allow to cool to room temperature before serving, approximately 1 1/2 to 2 hours.