Preheat your oven to 375°F and place your pie crust into a 9-inch pie dish. Set aside.
In a large skillet or saucepan, melt the butter over medium heat. Add onion, carrots, and celery and cook until softened, about 5–7 minutes. Stir in garlic and cook for another 30 seconds.
Sprinkle the flour over the veggies and stir well. Cook for 1–2 minutes to get rid of the raw flour taste.
Slowly whisk in the chicken broth and milk. Stir constantly until the mixture thickens into a creamy, cozy sauce.
Add shredded chicken, seasonings, and all your veggies. Simmer for 2–3 minutes. Taste and adjust salt and pepper like the kitchen wizard you are.
Pour the filling into your prepared pie crust.
In a small bowl, mix breadcrumbs, Parmesan, melted butter, parsley, and salt. Sprinkle generously over the filling.
Bake for 30–35 minutes, until the topping is golden and the filling is bubbly and smells like emotional support.
Let cool for 10–15 minutes before serving… unless you enjoy burning the roof of your mouth like we did in the frozen pot pie era.