Preheat oven to 375°. Line 2 baking sheets with parchment paper. Beat egg and water together in a small bowl. 

For the Crusts: Place 1 pie crust on a lightly floured work surface. Sprinkle the top with flour and roll the dough to 1/16-inch thickness (about the thickness of a flour tortilla). Using a 16 oz. deli container lid or a 28 oz. can of tomatoes (about 4 1/2 inches diameter), cut out as many rounds as possible. Transfer the rounds to a baking sheet in a single layer, gather the dough scraps into a ball and refrigerate both. Repeat with the second crust and the second baking sheet. Gather all the dough scraps together into a ball and re-roll the dough as needed until you have 16 rounds total, 8 on each baking sheet. Refrigerate while you make the filling.

For the Filling: Place the potatoes in a bowl and coarsely smash with a potato masher. Stir in the curry. Gently mix in the peas & carrots and green onions.

Work with one sheet of crusts at a time, keeping the other in the refrigerator until ready to fill. Place 2 level Tbsp. of the filling in the center of each crust. Dip your finger in the egg wash and trace around the edge of the crust to moisten. Place the hand pie in your hand and fold the sides up like a taco. Pinch the bottom left and right sides together at the edges, and then continue pinching towards the middle until the entire hand pie is sealed. Lay the hand pie flat on the baking sheet, and press the tips of fork tines along the rounded edge to seal. Brush the tops with egg wash. Bake until golden brown, 30 minutes.

Meanwhile, fill and seal the second sheet of hand pies. Serve warm or at room temperature.