Make Pie Crust by Hand: (see here for instructions for making it in a food processor)

1. In a large bowl, whisk together the flour, cornstarch, and salt.
2. Toss in butter and coat with flour. Using your fingers, squeeze and work the butter into the flour. Continue until most of the butter looks shaggy. Some larger pieces can remain, up to the size of a marble.
3. Add the vinegar to the water, then drip in 3/4 of it throughout the dough, and toss together with your fingers. If there is enough water, the dough should easily squeeze together with your hands. Drip in more water as needed, switching to a spatula if needed to moisten any dry spots. Add just enough water to bring the dough together.
4. Using your hands, gently bring the dough together as one large mass. Transfer the pastry to a work surface and divide it into two pieces, each about 12 ounces. Shape each piece into a rough disk shape.
5. Place each disk in a piece of plastic wrap and wrap tightly.
6. Using a rolling pin, roll the wrapped dough out until it stretches to the edges of the plastic wrap.
7. Refrigerate for at least 4 hours, but preferably overnight.

Make the Peach Filling:

1. Combine the sugar, cornstarch, and nutmeg in a medium bowl. Whisk together. Add in the peaches and lemon juice and gently toss together with a rubber spatula.
2. Let sit until the sugar has started to dissolve, about 10 minutes.
3. Transfer the mixture to a large pot.
4. Turn the heat on to medium and cook, stirring frequently, until the filling is bubbling throughout, about 10 minutes.
5. Remove from the heat and stir in the butter and almond extract.
6. Pour into a shallow container and let cool completely (this will take several hours or overnight). 

Assemble and Bake:

1. Make egg wash by whisking together the egg and the water together in a bowl.
2. Line a 12x18” sheet pan with a piece of parchment paper.
3. Roll out 1 disk of pie dough to about ⅛” thickness. Cut out at least six 4” circles from the dough. Pile the dough scraps on top of one another and roll out again, enough to get at least 1-2 more circles. Repeat this process with the other dough disk to yield 16-18 dough circles total.
4. Brush the egg wash around the edges of 1 pie dough circle. Place about 3-4 tablespoons of the cooled peach filling in the middle. Place a second pie dough circle over the top and press down on the edges to seal the two pieces together. Crimp the edges of the bottom to the top to further seal the pie and to add a decorative touch.
5. Place the pie on the sheet pan. Repeat with the remaining dough circles. When finished assembling, place the sheet pan in the freezer to chill while the oven preheats. Set aside the leftover peach filling, as you’ll need some of it for the glaze.
6. Preheat the oven to 400ºF and set a rack to the second-lowest position in the oven.
7. Remove the pies from the freezer, brush the tops with an egg wash and sprinkle with coarse sugar.
8. Bake for 30-40 minutes, or until the pie dough is lightly golden all over.
9. Remove the pies from the oven and let them cool slightly before transferring to a cooling rack.
10. Meanwhile, make the optional glaze: Spoon out about 2-3 tablespoons of the juicy liquid from the leftover peach filling and add it to a small bowl. Whisk in ¾ cup powdered sugar. If the glaze is too thick, add in another tablespoon of peach filling, and if it’s too thin, add in more powdered sugar.
11. Place one tablespoon of glaze in the middle of the cooled hand pie and gently smooth it out into an even layer.