Active Time: 1 hour, 15 minutes
Total Time: 3 hours, 35 minutes
Serves: 6 to 8
The dough can be made and refrigerated two days ahead—and can also be frozen for up to six months (thaw completely before using).
Ingredients
Crust
1 stick unsalted butter
1¼ cups unbleached all-purpose flour, plus more for dusting
½ teaspoon kosher salt
Filling
1 whole chicken (3½ pounds), quartered
2 leeks, white and pale-green parts thinly sliced (2 cups), 6 dark-green tops reserved
3 stalks celery, 1 halved, 2 chopped (¾ cup)
8 ounces cremini mushrooms, stems removed and reserved, caps coarsely chopped
½ small butternut squash, seeded, peeled, and chopped (2½ cups), peelings reserved
Kosher salt and freshly ground pepper
4 cups low-sodium chicken broth
6 tablespoons unsalted butter
⅓ cup unbleached all-purpose flour
1 tablespoon fresh thyme leaves
½ cup dry white wine, such as Sauvignon Blanc
1 cup frozen peas, thawed
½ cup packed chopped fresh flat-leaf parsley leaves
1 large egg white
Directions
1. Crust: Brown butter in a medium saucepan; let cool completely. Pour into an ice-cube tray, filling cups halfway. Freeze until cold and firm about 1 hour. Pulse flour and salt in a food processor to combine. Add chilled brown butter; pulse until mixture resembles coarse meal with some pea-size lumps. Drizzle with 3 tablespoons ice water. Pulse until mixture just begins to hold together. (If mixture crumbles when squeezed in your hand, drizzle with 1 more tablespoon ice water and pulse a few more times.) Transfer to a piece of plastic wrap; knead just until dough holds together. Loosely cover and shape into a disk. Wrap tightly and refrigerate until firm, about 1 hour.
2. Filling: Meanwhile, combine chicken, reserved leek tops, halved celery, mushroom stems, squash peelings, and 1 tablespoon salt in a large pot. Add broth and enough water to just cover chicken. Bring to a boil, then reduce heat to medium and simmer until a thermometer inserted into thickest parts of chicken (without touching bones) registers 160°, about 20 minutes. Transfer chicken to a plate. Strain broth; reserve 2½ cups (refrigerate or freeze remainder for another use).
3. Brown butter for filling in pot. Add sliced leeks and chopped celery, mushroom caps, and squash; season with salt and pepper. Cook, stirring occasionally, until squash begins to soften, about 5 minutes. Stir in flour and thyme; cook until darkened slightly and nutty, about 2 minutes. Add wine; boil until mostly evaporated, about 30 seconds. Stir in reserved broth and bring to a boil, then remove from heat. Pull chicken from skin and bones and tear into bite-size pieces. Stir into pot with peas and parsley. Transfer to a 3-quart baking dish. (Filling can be made up to 2 day ahead and refrigerated; stir in peas and parsley just before baking.)
4. Preheat oven to 400°. On a floured work surface, roll out dough to a diameter slightly larger than baking dish. Center dough over filling; trim edges to a ½-inch overhang. Beat egg white with 1 teaspoon water; brush over dough. Cut vents in center. Bake until crust is golden brown and filling bubbles, 35 to 45 minutes. Let cool 20 minutes before serving.