Prepare either pie crust recipe through step 5.

Stir the blueberries, sugar, flour, cornstarch, cinnamon, lemon juice, and lemon zest together in a large bowl. Mix together until it’s no longer dry and powdery; burst a few blueberries if necessary to moisten. Set filling aside as the oven preheats. Filling can be covered and refrigerated for up to 24 hours if needed.

Adjust the oven rack to the lower third position and preheat to 425°F (218°C). Place baking sheet on the bottom oven rack to catch any blueberry juices.

On a floured work surface, roll out one of the discs of chilled dough (keep the other one in the refrigerator). Turn the dough about a quarter turn after every few rolls until you have a circle 12 inches in diameter. Carefully place the dough into a 9 x 1.5 or 2-inch round pie dish. Tuck it in with your fingers, making sure it is smooth. Pour and spread filling evenly into pie dish. Dot the pieces of butter on top of the filling. Set aside at room temperature or in the refrigerator as you assemble the top pie crust.

Remove the other disc of chilled pie dough from the refrigerator. Roll the dough into a circle that is 12 inches diameter. Using a pastry wheel, sharp knife, or pizza cutter, cut strips of dough; in the pictured pie, I cut 10 1-inch-wide strips. Carefully thread the strips over and under one another, pulling back strips as necessary to weave. (Here’s a lattice pie crust tutorial if you need visuals.) Press the edges of the strips into the bottom pie crust edges to seal. Use a small paring knife to trim off excess dough. Flute or crimp the pie crust edges with a fork.

Lightly brush the top and edges of the pie crust with egg wash. Sprinkle the top with coarse sugar, if using.

Bake the pie at 425°F for 25 minutes; then, keeping the pie in the oven, reduce the oven temperature down to 375°F (190°C). Place a pie crust shield (see Note for homemade shield) on the edges to prevent them from over-browning. Continue baking the pie until the filling’s juices are bubbling everywhere, including in the center, 40–50 more minutes. This sounds like a long time, but under-baking the pie means a soupy filling with paste-like flour and cornstarch chunks. If you want to be precise, the internal temperature of the filling taken with an instant read thermometer should be around 200°F (93°C) when done. Tip: If needed towards the end of bake time, remove the pie crust shield and tent an entire piece of foil on top of the pie if the top looks like it’s getting too brown.

Remove pie from the oven, place on a cooling rack, and cool for at least 4 hours before slicing and serving. Filling will be too juicy if the pie is warm when you slice it.

Cover leftovers tightly and store in the refrigerator for up to 5 days.