1. Preheat oven to 400°F (200°C).

2. In a large bowl whisk 2 1/2 cups flour with 1/2 teaspoon salt.

3. Cut in 1 cup cold cubed butter until mixture resembles pea-sized pieces.

4. Stir in 1/2 cup sourdough discard and 3 tablespoons cold water until dough forms, adding more water if needed.

5. Shape dough into a disk, wrap it in plastic, and chill for at least 30 minutes.

6. In a skillet melt 2 tablespoons butter and sauté onion, carrots, and celery until softened, about 5 minutes.

7. Stir in 1/4 cup flour and cook for 1 minute, then gradually whisk in broth and cream until thickened.

8. Add turkey, peas, thyme, sage, salt, and pepper and simmer for 3 to 4 minutes.

9. Roll out chilled dough to fit a 9-inch pie dish, transfer the bottom crust, and trim edges.

10. Fill with turkey mixture, roll out and place top crust, seal and vent, then brush with egg wash.

11. Bake for 35 to 40 minutes until golden brown and bubbling, then rest for 10 minutes before serving.