Combine 313g all-purpose flour, 230g spelt flour, and 1 tsp Kosher salt in the bowl of a food processor fitted with blade attachment, then pulse to combine. Add 227g unsalted butter and 167g shortening, then pulse until pea-sized pieces remain.
Add 6 Tbsp ice water and pulse until the dough pulls together. Continue adding an additional tablespoon of water, as needed, until the dough forms. I usually stop at 8 Tbsp.
Remove the dough and separate into 2 equal disks. Wrap each tightly in plastic wrap, then refrigerate for 30 minutes.
Preheat oven to 375 F. Combine 7 cups of berries, 100g sugar, 34g flour, 1 Tbsp lemon juice, 2 tsp lemon zest, and ¼ tsp Kosher salt in a large bowl, then toss gently to combine.
Roll out 1 disk of pie dough on a lightly floured surface, then carefully transfer to a 15" x 10" x 1" sheet pan. The dough should be about 2" longer than your pan on either side — so about 17" x 12". Use your hands go lightly press the dough into the bottom and up the sides, allowing any excess dough to hang over the edge. If the dough breaks to tears, simply use your hands to press it back together — this dough is very forgiving! Refrigerate until needed.
Pour the mixed berries into the prepared pie dough and spread into an even layer.
Roll out the remaining pie dough on a lightly floured surface. At this point you can transfer the entire dough over to the sheet pan for a fully covered pie, or you can cut the dough into long strips and create a lattice pattern.
place half the strips diagonally across the sheet pan. Weave the remaining strips to form a lattice pattern.
Trim edges so that the dough is even with the sides of the pan, tucking the bottom dough over the top dough as needed, then use your fingers or a fork to crimp or pattern dough along the sides.
Brush the top of the pie with a beaten egg, then sprinkle with a couple tablespoons of turbinado sugar. Bake for 40-45 minutes, or until the crust is a deep golden brown and the berries are bubbling. Allow the pie to cool for 1 hour before slicing and serving with your favorite ice cream or homemade whipped cream.