In a large mixing bowl, combine 2 cups of all-purpose flour, 1 tsp of salt, 1-2 tbsp of sugar, and ⅛ tsp of baking powder. Cut 1 cup of shortening into the mixture using a pastry cutter until it resembles coarse crumbs. Gradually add ½ cup of cold water, mixing until a dough forms. Divide the dough in half, shape into discs, wrap in plastic, and chill in the refrigerator for at least 30 minutes.

While the crust chills, prepare the filling by tossing together 5 cups of mixed berries with 1 cup of granulated sugar, ⅓ cup of Clearjel or tapioca starch, a dash of salt, and 1 tbsp each of orange and lemon juices. Stir until evenly coated and let sit for about 10 to 15 minutes.

Preheat your oven to 375°F (190°C). Roll out one chilled dough disc to fit a 9-inch pie pan. Transfer the rolled dough into the pan and pour in the berry mixture. Roll out the second dough disc and create a lattice design on top, sealing the edges. Brush the lattice with an egg wash and sprinkle with sugar.

Bake for 45 to 50 minutes until the crust is golden brown and the filling bubbles through the lattice. Rotate the pie halfway through baking. Cover the edges with foil if they darken too quickly.

After baking, let the pie cool on a wire rack for about 20 to 30 minutes before slicing. Serve warm or at room temperature, optionally with vanilla ice cream.