Preheat oven to 425 degrees F.

Season chicken with salt and pepper. Add the chicken to a large saucepan and cover with 2 cups chicken broth. Bring it to a simmer and cook until it’s just barely cooked through then remove the chicken to a plate. Reserve chicken broth in a measuring cup.

Add onions, celery, carrots and butter to the saucepan and cook for a few minutes, until soft and translucent. Stir in the flour, salt, pepper, garlic powder, bullion and celery seed.

Slowly stir in the reserved chicken broth and milk. Simmer over medium-low heat until thick.

Chop the cooked chicken and add it to the pot along with the frozen peas. Taste and season with more salt, pepper, bouillon or garlic powder if needed. Allow mixture to cool (so that’s it’s not hot when poured into the pie crust).

Once cooled, pour mixture into bottom pie crust. Cover with top crust, seal edges, and cut away excess dough. Make a few small slits in the top crust to allow steam to escape.

Make egg wash by whisking 1 egg with 1 tablespoon milk and lightly brush over the top pie crust before baking.

Bake for 40-50 minutes, or until the top crust is golden brown and filling is bubbly. If you find the pie crust is browning too quickly, cover it with foil. 

Cool for at least 20-30 minutes before serving to allow it to set up.