• Preheat the oven to 375°F (190°C).

Make the Crust:

• In a large bowl, combine the flour and salt.
• Add the cold butter and shortening, and use a pastry blender or your fingers to work the fat into the flour until the mixture resembles coarse crumbs.
• Gradually add the ice-cold water, stirring with a fork until the dough comes together in a ball.
• Divide the dough in half, and shape each half into a disk.
• Wrap each disk in plastic wrap, and refrigerate for at least 30 minutes.

Make the Filling:

• In a separate large bowl, combine the blueberries, granulated sugar, cornstarch, lemon juice, salt, cinnamon, and nutmeg.
• Stir in the melted butter until the mixture is well combined.

Assemble the Pie:

• Roll out one of the chilled dough disks to a thickness of about 1/8 inch.
• Place the dough into a 9-inch pie dish, and trim the edges to fit.
• Fill the pie crust with the blueberry mixture, and dot the top with the remaining butter.

Roll out the second dough disk to a thickness of about 1/8 inch:

• Use a pastry cutter or a knife to cut the dough into strips for a lattice-top crust.
• Place the strips on top of the pie, weaving them into a lattice pattern.
• Trim the edges of the strips, and press the edges of the lattice to seal.

Bake the Pie:

• Bake the pie for 40-50 minutes, or until the crust is golden brown and the filling is bubbly.
• Cover the edges of the pie with foil if they begin to brown too quickly.

Cool the Pie:

• Allow the pie to cool on a wire rack for at least 30 minutes before serving.