If using homemade pie crust, make two crusts the night before as they need an hour to chill before using. Keep refrigerated until right before it is time to roll them out and fill the pie.
2 pie crusts
Melt the butter in a large skillet or Dutch oven. Add the carrots, celery, onion, and garlic. Season with salt and pepper and sauté until the vegetables are soft, about five to seven minutes.
4 tablespoons unsalted butter, 2 large carrots, 2 celery stalks, 1 small yellow onion, 2 cloves garlic, 1 teaspoon kosher salt, 1/2 teaspoon black pepper
Whisk in the flour. Then slowly whisk in the chicken broth, scraping up any browned bits. I like to whisk in the broth a few tablespoons at a time, adding more when what I just added has been absorbed. That being said, whisking it in should take less than a minute. Whisk in the milk, thyme, and add in two bay leaves. Bring to a simmer.
1/2 cup all purpose flour, 2 1/2 cups chicken broth, 1 cup milk, 1/2 teaspoon dried thyme, 2 bay leaves
Add in the chicken and cook for 10 minutes or until the chicken is cooked through, stirring occasionally so it does not stick to the bottom of the pot. Discard the bay leaves and stir in frozen peas. Allow the filling to cool in the refrigerator for 30 minutes. (Alternatively, you can make your filling the night before.)
1 pound boneless skinless chicken breasts, 1 cup frozen peas
Preheat your oven to 375 degrees Fahrenheit.
Roll out the pie crust dough. Line the bottom of a deep dish pie pan with one rolled out pie doughs. Add the chilled filling. Top with the second pie crust. Crimp the edges and brush the crust with the egg white. Cut a few holes for steaming. Bake for 30 to 40 minutes or until the pie crust is golden brown. Allow to cool for 45 to 90 minutes before slicing.
2 pie crusts, 1 egg white