To make the crust, add flour, salt, baking powder, salt and sugar to a food processor and pulse a few times to combine.

Add the cubed butter to the food processor and pulse a few times until coarse crumbs form.

With the motor running, pour iced water and cider vinegar and pulse a few times until the dough just forms into large clumps.

Turn out the dough onto a floured surface and gently knead until it comes together.

Flatten the dough into disk.

Wrap disc with plastic wrap and refrigerate for at least 2 hours.

Add the blackberries, sugar, lemon juice, lemon zest and cornstarch to a bowl and stir to combine.

Set aside.

Line a baking sheet with parchment paper or silicon mat.

On a lightly-floured surface, roll out disk until it is 1/8 inch-thick.

Use a 5-inch biscuit cutter to cut out circles of dough.

Re-roll any scraps to make more circles.

Spoon about 3 tablespoons of blackberry filling onto each circle, leavening 1 inch border around the rim.

Fold the dough in half over the filling.

Pinch the dough with your fingers to seal tightly.

Place the pies on the prepared baking sheet.

Cover with plastic wrap and refrigerate for 1 hour.

Preheat oven to 350ºF.

Brush the pies with beaten eggs.

Cut three slits into the top of each hand pie.

Bake in preheated oven for 20-25 minutes or until golden.

Remove form the oven and allow to cool for 10 minutes.

Serve warm.