Make the pie dough. In the bowl of a food processor, pulse together 2 ¼ cups flour, 2 tsp sugar, and ½ tsp Kosher salt. Add ½ cup cold butter and 7 Tbsp shortening, then pulse until small, pea-sized pieces form. Add 4 Tbsp of ice water, then pulse, adding the last Tbsp as needed, until the dough begins to come together.
Chill pie dough. Dump the dough out onto a sheet of plastic wrap and roll into a flat disk. Chill for at least 30 minutes. If you leave the dough in the fridge longer than that, it may need to sit out at room temperature until it is easier to roll out.
Make the blueberry galette filling. In a large bowl, combine 2 cups blueberries, ⅓ cup sugar, 1½ Tbsp cornstarch, 1 Tbsp lemon juice, ½ tsp lemon zest, ¼ tsp cinnamon, and ¼ tsp Kosher salt. Stir gently to combine, being careful not to burst the blueberries. Set aside.
Roll out the dough. Remove dough from refrigerator and use a pastry scraper or a knife to cut into 6 equal pieces (one horizontal cut and then two vertical). Roll one portion of dough out onto a lightly floured surface until it’s roughly 7-8 inches in diameter. Repeat with remaining portions of dough.
Form the galettes. Line a rimmed baking sheet with parchment paper, then transfer over the rolled out dough. It’s okay if the pieces overlap for now. Place about ¼ cup of filling in the center of each dough round, leaving the outer 1” untouched. Gently fold over the edges of the dough onto the filling, overlapping the edges as you go. Repeat until all galettes are formed.
Bake the blueberry galettes. Brush egg wash on top of dough, then sprinkle each with Turbinado sugar. Bake at 425°F / 220°C for 16-18 minutes, or until filling is bubbly and crust is a deep golden brown. Let cool for 5 minutes, then serve warm with ice cream (we recommend coffee!) or fresh whipped cream.