Pulse together the flour and salt in a food processor. Add the butter and pulse until it looks like coarse meal (the pieces of butter should be about the size of small peas). (Alternatively, this can be done by hand; whisk the flour and salt together in a large bowl, then cut in the butter with a pastry cutter or a fork until it looks like coarse meal.)
Transfer the dough from the food processor to a large bowl. Add 1 tablespoon water at a time, working the dough together with your fingertips just until it comes together, and only adding enough water so the dough comes together when you squeeze it.
Divide the dough into 8 equal pieces and place them in a large bowl, cover with plastic wrap, and refrigerate until chilled, about 30 minutes.
While the pastry dough chills, stir together all filling ingredients in a large bowl; set aside.
To Assemble the Pasties:
Preheat the oven to 400F. Line 2 large baking sheets with parchment paper or silpat liners.
Working with 1 ball of dough at a time, roll it out on a floured surface to a circle about 8 inches in diameter. Use a plate as a guide to trim the edges so you have a perfect circle.
Spoon about 1/2 cup of filling into the center of the dough; lightly brush the edge of the dough with eggwash. Fold both sides of dough up over the filling and crimp the edges together in the center of to form a tight seal.
Continue this way until 8 pasties are assembled, then if there is filling leftover, re-roll the dough scraps and continue making pasties until you run out of filling or dough (I usually get 9 pasties out of this recipe).
Arrange the pasties onto the prepared baking sheets and lightly brush each with eggwash.
To Bake the Pasties:
Bake at 400F for 15 minutes, rotating the trays once halfway through.
Reduce the heat to 350F and bake until the crusts are golden brown, about 30 minutes more, rotating the trays once halfway through.
Serve warm or at room temperature.
Serving Tip: You can serve pasties warm or at room temperature.
Storage and Reheating: Store leftover pasties covered in the fridge for up to 3 days. To reheat, place them on a baking tray and heat in a 350F oven until warm throughout, about 10 to 15 minutes.