Start by making the dough. In a large mixing bowl, whisk together the flour, sugar, and salt. Sprinkle cold cubed or grated butter over the flour mixture. Use your fingertips or a pastry cutter to cut butter into the flour until incorporated (butter should be about pea-sized).

Slowly drizzle in the ice water and stir until a soft dough forms. You may need to get in with your hands to fully incorporate the water. The dough should easily come together and not feel sticky. Form dough into a disc and tightly wrap with plastic wrap. Refrigerate for 1 hour (this is important).

Line a large baking sheet with parchment paper. Preheat oven to 350℉. 

Remove the dough from the fridge and transfer to a lightly floured surface. Roll dough into a 12-inch circle. Transfer the dough circle to the prepared baking sheet.

In a large bowl, combine the blueberries, sugar, cornstarch, lemon zest and juice, and vanilla. 

Spoon the fruit into the center of the dough (leaving a 3" border along the edges). Gently fold the edges of the dough over the filling, overlapping the dough as you do it. Brush the dough with the egg wash and sprinkle the crust with raw sugar.

Bake galette until golden brown, for about 30-40 minutes. Cool on the baking sheet for 10 minutes before serving. Serve warm with vanilla ice cream.