Step 1: Prepare the Crust

• In a large mixing bowl, whisk together the flour, powdered sugar, and salt.
• Add the chilled, cubed butter and mix until the mixture resembles coarse crumbs.
• In a separate bowl, combine the blueberry puree and egg yolk. Add this to the flour mixture and stir until just combined.
• Gradually add cold water, one tablespoon at a time, until the dough comes together. Divide the dough into two equal parts, flatten into discs, and wrap in plastic wrap. Refrigerate for at least 1 hour.

Step 2: Make the Apple Filling

• In a large bowl, combine the sliced apples, granulated sugar, lemon juice, cinnamon, nutmeg, cornstarch, and vanilla extract. Toss until the apples are well coated and let sit for 15 minutes.

Step 3: Roll Out the Dough

• Preheat your oven to 425°F (220°C).
• Remove one dough disc from the refrigerator and roll it out on a floured surface to fit your pie pan. Transfer the rolled dough to the pie pan and trim any excess.

Step 4: Fill the Pie

• Pour the apple filling into the prepared pie crust, spreading it evenly.

Step 5: Add the Top Crust

• Roll out the second dough disc and place it over the apple filling. You can cut slits for a lattice effect or simply leave it whole. Trim and crimp the edges to seal the pie.
• Optional: Brush the top with an egg wash (1 egg beaten with 1 tablespoon water) for a golden finish.

Step 6: Bake the Pie

• Bake the pie in the preheated oven for 15 minutes, then reduce the temperature to 350°F (175°C) and continue baking for an additional 30-35 minutes, or until the apples are tender and the crust is golden brown.

Step 7: Cool and Serve

• Allow the pie to cool for at least 30 minutes before slicing. This will help the filling set and make for cleaner slices.