Preparation

• Prepare either pie crust recipe through step 5, including chilling for at least 2 hours.
• Place ½ cup of each type of berry in a medium bowl and set aside.
• Place the remaining 2 and ½ cups blueberries, 1 cup raspberries, and 1 cup blackberries in a medium saucepan over medium heat. Add sugar and cinnamon and cook until berries release juice.
• Mix cornstarch and lemon juice in a small bowl, then add warm berry juice to the mixture to create a smooth paste.
• Stir the cornstarch mixture into the saucepan and cook until thickened, about 5–7 minutes.
• Remove from heat, stir in reserved berries, lemon zest, and vanilla. Let cool for 20 minutes.
• Adjust oven rack to lower third position and preheat to 425°F (218°C). Place a baking sheet on the bottom rack.
• Roll out one disc of chilled dough on a floured surface to form a 12-inch circle and place in the pie dish.
• Fill the crust with the berry mixture and refrigerate while rolling out the top crust.
• Roll out the second disc into a 12-inch circle and cut into 1-inch-wide strips to create a lattice top.
• Thread the strips over and under to weave the lattice, sealing edges with the bottom crust.
• Brush with egg wash and sprinkle with coarse sugar if desired.
• Bake at 425°F for 20 minutes, then reduce temperature to 375°F (190°C) and bake for an additional 45–55 minutes.
• Remove from oven and cool on a rack for at least 5 hours before slicing.
• Cover and store leftovers in the refrigerator for up to 5 days.