01 -
In a large bowl, mix flour, sugar, and salt. Add cold cubed butter; toss to coat. Transfer mixture to a clean work surface. Using a rolling pin, press and roll the butter into thin sheets, incorporating into the flour. Gather with a bench scraper as needed until butter is fully integrated, creating a flaky mixture. Return to bowl and freeze for 15 minutes.
02 -
Remove mixture from freezer. Add cold buttermilk, stirring with a spoon, then by hand, until dough begins to come together. Add cold water gradually, only if needed. Divide dough in half, shape into disks, wrap in plastic, and refrigerate while preparing the filling.
03 -
In a large skillet over medium-high heat, melt butter. Add onions, carrots, celery, and garlic; cook until vegetables are just tender. Sprinkle in flour, salt, pepper, thyme, and parsley. Stir well. Gradually whisk in chicken broth and heavy cream until smooth. Reduce heat and simmer for 10 minutes, or until sauce thickens. Stir in chicken and peas. Remove from heat.
04 -
Preheat oven to 200°C. Remove dough from refrigerator. On a lightly floured surface, roll one disk into a 30 cm circle, about 6 mm thick. Transfer to a 23 cm pie dish, smoothing gently and trimming excess edges.
05 -
Fill the prepared pie crust with the chicken filling. Roll out the second dough disk and cover the pie, trimming extra dough. Seal edges by crimping with a fork or by hand. Slice a few small slits in the center to vent steam. Brush crust and edges with beaten egg.
06 -
Bake for 45 minutes, or until crust is golden brown. Shield the edges with foil or a pie crust guard if browning too rapidly. Allow to cool 10 minutes before slicing and serving.