In a large bowl, combine the chopped carrots, chopped celery, diced onion, peas (if using), diced garlic and parsley. In a large saucepan melt the butter over medium heat. Add in the vegetable mixture. Stir to coat the veggies with the melted butter and cook them over medium heat until they begin to soften, about 10 minutes.
Sprinkle the ⅓-cup of flour over the top and stir into the mixture. Cook the mixture for 1 minute more, and then slowly add in the chicken stock and milk. Bring the mixture to a simmer and simmer it, stirring frequently until the liquid has thickened a little, about 3 minutes. Remove the pan from the heat. Stir in the chicken, salt and pepper. Set the mixture aside to cool.
Prepare the dough:
Take half of the chilled All-Butter Pie Crust Dough and use a knife or bench scraper to cup the dough into 6 equal pieces.
On a lightly floured surface, roll each portion into an 8-inch circle. Fit each circle into a mini aluminum pie tin, pressing the dough over the bottoms and up the sides of the tins, and allowing excess dough to hang over the sides.
Check the temperature of the filling: it should be lukewarm or cooler. (Any warmer than this and it will start to melt the butter in the dough as you fill the pies.) If the filling is not yet cool enough, loosely cover the dough in the tins with plastic wrap and refrigerate them while you wait.)
Assemble the pies:
Once the filling is cool enough, preheat the oven to 425° F. Move the rack to the lower half of the oven. Have a large baking sheet ready to set the pies on.
Add a generous cup of chicken-vegetable filling to each of the pie shells. If you still a little filling left, divide evenly between the pies.
Take the other half of the All-Butter Pie Crust from the fridge and divide it into 6 equal portions. On a lightly floured surface, roll each portion out into a 6-inch circle.
Place a dough circle on top of one of the pies. Trim the edges to be just slightly larger than the overhang of the bottom crust.
Roll both the lower and upper crust edges under, all around the pie to make a thick edge. Firmly crimp the edge all around onto the edge of the tin.
Cut a few slits in the top crust for venting. Repeat these steps for the other 5 pies.
Note: if you're planning to freeze the pies, skip the next step and refer to the Freezer Directions at the end of the recipe.)
Beat together the egg plus ¼ cup water. Brush this egg wash over the tops of the pies using a pastry brush. Sprinkle a few Maldon sea salt flakes over each pie.
Place the pies on the baking sheet and pop them into the oven. Bake the pies for 30 minutes, until the crusts are nicely browned and the filling is bubbling. Serve the pies immediately.
Wrap the assembled pies in a few layers of plastic wrap and set them in a single layer in your freezer. Once they are frozen solid you can stack them, and keep them in the freezer for up to one month.
When ready to bake them, preheat the oven to 400° F, and move the rack to the lower half of the oven. Unwrap the frozen pies and place them on a baking sheet.
Beat together an egg plus ¼ cup water. Brush this egg wash over the tops of the pies using a pastry brush. Sprinkle a few Maldon sea salt flakes over each pie.
Bake the pies for about 50 minutes, until the centers are cooked through and bubbling, and the crust has browned. (If the crust is browning too quickly, you can tent the top with a piece of aluminum foil.)
Option: Make Your Own Poultry Seasoning
To make your own poultry seasoning blend, stir together 1 teaspoon ground sage, 1 teaspoon thyme, ½ teaspoon marjoram, ½ teaspoon rosemary, and a dash each of ground black pepper and ground nutmeg.