1 egg yolk beaten with 1 teaspoon of water, to make a glaze
Preheat the oven to 400°. In a medium bowl, toss together the blueberries and orange zest. In a small bowl, mix together 1/2 cup of the sugar, the tapioca and the allspice.
On a lightly floured surface, roll out one of the pastry disks to an 11-inch round and fit it into a 9 1/2- to 10-inch pie dish without stretching. With a scissors, trim the pastry to within 1/2 inch of the edge of the pie dish.
Pour the blueberries evenly into the dish and sprinkle the sugar-tapioca mixture over the top.
Roll the remaining pastry disk into an 11-inch round. Drape the pastry over the berries and trim to within 1 inch of the edge of the dish. Tuck the edge of the pastry rim neatly under the bottom crust. Crimp the edge decoratively to seal. Cut a 5-inch cross in the center of the crust.
Brush the pie crust with the egg glaze and fold open the cross to form a square. Brush the turned-up pastry corners with glaze. Sprinkle the crust with the remaining 1 teaspoon sugar.
Set the pie on a baking sheet in the middle of the oven and bake for 50 minutes or until the pastry is golden and the sugar and tapioca are absorbed by the berries. If the pastry is browning too quickly, loosely cover the pie with a sheet of aluminum foil for the last 10 minutes.