1. Preheat the oven to 400°F (200°C).

2. In a large ovenproof skillet, melt butter over medium heat and sauté onion, carrots, and celery until vegetables soften, about 5–7 minutes.

3. Stir in flour and cook for 1–2 minutes to form a roux, stirring constantly.

4. Slowly whisk in broth and milk, stirring until the sauce thickens, about 5 minutes.

5. Add turkey, peas, thyme, parsley, salt, and pepper; stir to combine and adjust seasoning.

6. In a bowl, mix flour, baking powder, baking soda, and salt; cut in cold butter until mixture resembles coarse crumbs.

7. Stir in buttermilk until just combined, then fold in cheddar if using.

8. Roll dough to 3/4 inch thickness and cut biscuits, or drop dollops of dough over filling for a rustic look.

9. Arrange biscuits over the filling, brush with melted butter, and bake for 25–30 minutes until biscuits are golden and filling bubbles.

10. Let the pot pie rest for 10 minutes before serving to thicken the filling.