Turkey Potpie

Directions

1. 1
   Wash chopped leek well in a bowl of cold water, agitating it, then lift out and drain well.
2. 2
   Bring all stock ingredients to a boil in a 4- to 5-quart saucepan, skimming froth, then reduce heat and gently simmer, partially covered, until reduced to about 4 cups, about 1 1/4 hours.
3. 3
   Pour stock through a large sieve into a bowl.
4. 4
   Transfer turkey to a cutting board to cool.
5. 5
   Discard remaining solids.
6. 6
   When meat is cool enough to handle, coarsely shred from bone, discarding skin, and set aside.
7. 7
   Blend together flour, cornmeal, butter, and salt in a bowl with your fingertips or a pastry blender (or pulse in a food processor) until most of the mixture resembles coarse meal with some roughly pea-size butter lumps.
8. 8
   Drizzle evenly with 3 tablespoons ice water and gently stir with a fork (or pulse in processor) until incorporated.
9. 9
   Squeeze a small handful: If it doesn't hold together, add more ice water, 1 tablespoon at a time, stirring (or pulsing) until just incorporated, then test again.
10. 10
    (Do not overwork, or pastry will be tough.)
11. 11
    Turn out mixture onto a lightly floured surface and divide into 2 portions.
12. 12
    With heel of your hand, smear each portion once or twice in a forward motion to help distribute fat.
13. 13
    Gather dough together with scraper and press into a ball, then flatten into a 3-inch disk.
14. 14
    Chill dough, wrapped tightly in plastic wrap, until firm, at least 1 hour.
15. 15
    Heat oil in a 12-inch heavy nonstick skillet over moderately high heat until hot but not smoking, then saute onion, carrots, and celery, stirring occasionally, until golden, about 10 minutes.
16. 16
    Add mushrooms, potatoes, and garlic and saute, stirring, until vegetables are crisp-tender, about 10 minutes.
17. 17
    Remove from heat and stir in turkey, peas, and thyme.
18. 18
    Transfer filling to a 3- to 31/2-quart glass or ceramic baking dish.
19. 19
    Reheat stock in a 2- to 3-quart saucepan over moderate heat.
20. 20
    Transfer about 1/2 cup hot stock to a small bowl and whisk in flour, salt, and pepper until smooth.
21. 21
    Whisk flour mixture into remaining stock and boil until slightly thickened, about 5 minutes.
22. 22
    Pour sauce over filling in dish.
23. 23
    Put oven rack in middle position and preheat oven to 425F.
24. 24
    Roll out dough into a roughly 10- by 7-inch oval on a lightly floured surface with a lightly floured rolling pin, then place over filling and trim excess dough flush with edge of dish.
25. 25
    Brush with egg white, then bake until filling bubbles and crust is golden, about 30 minutes.
26. 26
    Transfer to a rack and cool slightly, about 10 minutes.