Prepare 2 crusts following my recipe here.

Toss in blueberries, flour, sugar, cinnamon, cornstarch, lemon zest, and lemon juice in a big bowl. Stir until mixed up. Squish some blueberries to moisten it if it's still dry or powdery. Optional: Cover this filling and refrigerate for 24 hours.

Prep the oven: Adjust its rack to the low third and crank to 425°F (or 218°C). Pop a baking sheet on another rack below to catch blueberry drips.

Flour up your work surface and roll out a chilled dough disc (keep another disc in the fridge) until you've got a nice 12-inch circle. Gently lay it into your 9-inch dish. Pour that pie filling into the dish evenly, then dot some butter pieces.

Bring out the other chilled dough disc from the fridge. Roll it out into a nice 12-inch circle. Slice that dough into strips.

Carefully weave those strips under and over each other. Press their edges against your bottom crust and cut out any extra dough. Use a small fork to crimp or flute those edges.

Brush the top crust lightly with egg wash for a golden finish. Optional: sprinkle on some coarse sugar.

Put it into the oven for 25 minutes, then lower the heat to 375°F (or 190°C). Slip a shield around the edges to keep them from getting too toasty.

Bake away until filling juices bubble all over the place (even in the middle!) (50 minutes). Or, stick a thermometer into the filling; around 200°F (or 93°C) is good to go.

Gently place your baked blueberry pie on a wire rack (out of the oven). Let it cool for 4 hours or even longer before slicing.