Preheat your oven to 400°F (200°C) with a rack positioned in the center.
In a large skillet over medium heat, melt the butter. Add the chopped onion, diced carrots, and celery, stirring occasionally until the onion is tender and translucent, about 5 minutes.
Add the minced garlic and cook for an additional minute until fragrant.
Sprinkle in the flour, kosher salt, black pepper, celery seed, and thyme. Stir continuously for about 2 minutes until a thick paste forms.
Gradually pour in the milk, stirring continuously. Slowly add the chicken stock while stirring until the mixture thickens, about 3 minutes.
Mix in the frozen peas and shredded chicken until well combined. Remove from heat.
Line a 9-inch pie pan with one pie crust. Spoon the chicken filling into the crust, making a slight mound in the center.
Brush the edge of the bottom crust with the beaten egg. Cover with the second pie crust, sealing securely, and crimp the edges. Cut two 2-inch slits in the top crust for steam to escape.
Brush the top crust with the remaining beaten egg for a golden finish.
Place the pie dish on a rimmed sheet pan and bake for 45-50 minutes, or until the crust is lightly browned and the filling bubbles. Allow to cool for 10-15 minutes before slicing and serving.
Send me this recipe!
Just enter your email below and get it sent straight to your inbox!
Notes
Store leftovers in an airtight container in the refrigerator for up to 3-4 days.