Start by peeling and dicing sweet potatoes into even chunks. Place them in a large pot and cover with water, adding a pinch of kosher salt. Bring to a boil, then reduce to a simmer for 16-18 minutes.

In a mixing bowl, add the drained sweet potatoes and mash until smooth and fluffy. Set aside to keep warm.

In a large skillet, heat olive oil over medium heat. Sauté shallots with parsley, thyme, and sage for 2-3 minutes.

Stir in chopped celery and cook for another 4-5 minutes until tender.

Add frozen peas and carrots, followed by the cooked turkey and broth. Season with salt and pepper. Simmer for 8-10 minutes.

Mix cornstarch with broth until smooth. Stir into turkey mixture and cook for 3-4 minutes until thickened.

Pour turkey filling into a baking dish, spread the sweet potato mash evenly on top.

Preheat oven to 375°F and bake for 20 minutes. Optionally broil for 2-3 minutes for a golden finish.

Let the pie sit for a few minutes before slicing and serving warm.