01 -
Combine flour, sugar, and salt in a large bowl. Add cold cubed butter and toss to coat. Transfer to a clean surface and roll the butter into the flour using a rolling pin, scraping and gathering the dough repeatedly with a bench scraper until incorporated and flaky. Chill mixture in freezer for 15 minutes.
02 -
Remove chilled mixture from freezer. Add cold buttermilk and stir with a spoon, then with hands, until dough forms a ball. Add cold water by tablespoon if too dry. Divide dough into two disks, wrap in plastic, and refrigerate while preparing filling.
03 -
Melt butter in large skillet over medium-high heat. Add onion, carrots, celery, and garlic; cook until tender, stirring occasionally. Whisk in flour, salt, black pepper, thyme, parsley, chicken broth, and heavy cream. Simmer over medium-low heat for 10 minutes until thickened. Stir in shredded chicken and peas then remove from heat.
04 -
Set oven to 400°F (204°C).
05 -
On lightly floured surface, roll one dough disk into 12-inch circle approximately 1/4 inch thick. Transfer to a 9-inch pie pan and smooth with fingers. Trim excess dough and discard.
06 -
Pour filling into crust-lined pan. Roll out second dough disk similarly and cover pie. Trim and seal edges by crimping. Cut small slits on top crust. Brush entire crust with beaten egg wash.
07 -
Bake pie for 45 minutes or until crust is golden brown. Use a pie crust shield if needed to protect edges. Cool for 10 minutes before slicing and serving.