1. Prepare the crust: Combine flour and salt in a large bowl. Cut in cold butter until the mixture resembles coarse crumbs. Gradually add ice water, one tablespoon at a time, tossing with a fork until the dough holds together. Divide dough into two disks, wrap tightly, and chill for at least 1 hour.

2. Prebake the bottom crust: Roll out one disk on a lightly floured surface to fit a 9-inch pie plate. Chill the rolled dough, then line the pie plate. Trim edges leaving an overhang. Freeze for 20 minutes. Bake at 375°F (190°C) for 20–25 minutes. Remove weights and parchment; cool completely.

3. Prepare the filling: Puree about 1 cup of blueberries with sugar, lemon juice, thickener, salt, and optional spices. Cook over medium-high heat until slightly thickened, about 1 minute. Mix in remaining blueberries gently.

4. Assemble the pie: Pour filling into the cooled crust and dot with butter. Roll out the second dough disk to 12 inches, place over the filling, trim, fold, and crimp edges. Brush with egg wash and chill for 20 minutes.

5. Finish and bake: Cut vents in the crust, apply egg wash, and sprinkle optional sugar. Bake at 400°F (200°C) for 30 minutes, reduce heat to 350°F (175°C), and bake for 25–45 minutes more. Use shields if needed.

6. Cooling: Cool the pie for at least 1 hour before slicing.