Pie crust dough, for two-crust pie
3 tablespoons cornstarch, sifted
3/4 cups sugar, plus as needed for garnish
2 cups blueberries, rinsed, picked over for stems, drained, and blotted dry
2 cups raspberries, rinsed, drained, and blotted dry
2 cups blackberries, rinsed, drained, and blotted dry
1/2 teaspoon freshly grated orange zest
Juice from one orange
1/4 teaspoon kosher salt
2 eggs, whisked together for egg wash
1. Make or purchase pie crust dough for a two-crust pie. Put the dough onto a lightly floured work surface and divide into two pieces. Shape into 5- to 6-inch disks, wrap tightly in plastic wrap, and chill in the refrigerator for a minimum of 45 minutes, or until firm. Roll out the bottom crust to a 12-inch diameter round that is 1/8-inch thick. Carefully lift and drape the dough in the pie pan and gently press in place. Trim the excess dough from the outer edge of the pan, and refrigerate until ready to use.
2. Preheat the oven to 375 degrees F. Combine the cornstarch with the 3/4 cup of sugar using a whisk to mix together thoroughly. Prepare the filling by gently, but thoroughly, tossing together the berries with the cornstarch and sugar mixture, orange zest and juice, and salt in a medium bowl. Pour the mixture into the bottom crust.
3. To prepare the lattice, roll out the top crust to a 12-inch diameter round that is 1/8-inch thick. Cut the round into 10 or more 1/2- to 3/4-inch strips. Lightly egg wash the outer rim of the bottom crust. Starting with a long strip in the center, gently arrange 5 strips going in the same direction over the top of the pie, spacing them evenly. Turn the pie 90 degrees and fold back alternating strips to slightly more than halfway. Place the first perpendicular strip onto the pie, slightly off center, and then carefully fold each strip back to the edge of the pan. Repeat, folding back the alternating strips and adding the next strip. Working back and forth, continue weaving by folding alternating strips back and unfolding them over added strips. Adjust as needed to make them even. Use a knife to trim off excess dough at the ends of the strips. Using the tines of a fork, press down along the edge of the pie to seal the top and bottom crusts together. Lightly egg wash the lattice and sprinkle lightly with granulated sugar to garnish.
4. Place the pie on a rimmed baking sheet, then onto an oven rack set in the center of the oven. Bake until bubbly and thick, approximately 45 to 50 minutes. Remove from the oven and place on a cooling rack for 2 to 3 hours. The filling will thicken as it cools.
Formulation courtesy of The Culinary Institute of America