Place 1 C butter (cut into chunks) in the freezer for 5 minutes.
In a food processor, combine the flour, salt and sugar with a few pulses.
Add the chilled butter and pulse until finely chopped.
Turn the speed on low and add one tbsp of ice water until the mixture comes together and holds when pinched.
Pour the flour mixture out onto a clean surface.
Gather into a dough ball and press to form a disc.
Divide the disc to form two equal parts.
Wrap the discs in plastic and place in the refrigerator for 1 hour.
Heat 2 tbsp olive oil in a Dutch oven or large pot over med/hi.
Saute the onion for one minute.
Add the carrots, celery and potatoes.
Saute 2 or 3 minutes.
Add 1 cup of chicken stock.
Add the dried sage and thyme.
Cover and turn heat to med/low.
Simmer until the veggies are soft when pierced with a fork.
Heat 1/4 cup butter in a medium skillet over med/hi.
When the butter is bubbling, add 1/4 cup flour and stir with a wire whisk for 2-3 minutes.
Add 1 cup chicken stock and continue stirring until no lumps remain and the mixture is smooth and creamy.
Remove from heat and pour into the veggie mixture.
Stir in the cooked chicken and peas (if desired).
Stir well and add salt and freshly ground black pepper to taste.
Remove from heat and set aside.
Preheat oven to 375 degrees F.
Take the pie crusts out of the refrigerator and allow to warm 15 minutes.
Place each piece on a well floured surface and sprinkle flour over top and onto a rolling pen.
Starting from the center, roll the dough out into a round by pressing away from you and turning a quarter inch each time you roll.
Each crust should be at least 11 inches in diameter.
Butter a 10 inch pie plate very well and place the bottom crust over top.
Press the bottom dough into the corners and up the sides.
Trim the edge of the dough to fit just over the rim.
Ladle the filling into the pie.
Place the top crust over the filling and trim off the excess, leaving 1 inch hanging over the sides.
Tuck the overlapping top crust under the bottom crust and pinch together.
Using your thumb and fingers, crimp the edge.
Cut 4 slits in the top of the crust.
Place the pie on a baking sheet and bake in the oven for 45 to 50 minutes until the crust is golden brown on top.
Remove from oven and allow to cool at least 20 minutes before serving.