- 2 pounds bone-in, skin-on chicken leg pieces (thighs and drumsticks)
- 1 medium onion, quartered
- 3 sprigs parsley
- 1 small bunch thyme
- 6 sage leaves, divided
- 3 tablespoons unsalted butter, divided
- 2 leeks, thinly sliced (about 1 cup)
- 2 tablespoons all-purpose flour
- 1/2 teaspoon Dijon mustard
- 1/4 cup cream
- Kosher salt and freshly ground black pepper
- 1 pound frozen puff pastry, thawed
- 1 egg, beaten
In a large pot, combine chicken leg pieces, onion, parsley, 1/2 bunch thyme, and 3 sage leaves, and cover with water. Bring to a simmer over medium high heat, reduce to low, cover, and cook until chicken is tender and falling off bone, about 1 hour. Remove and reserve chicken pieces, strain cooking liquid and reserve, and discard remaining solids. Return cooking liquid to pot and simmer until reduced to 1 1/2 cups, about 10 minutes. Reserve.
Shred the chicken and transfer to a large bowl, discarding skin and bones.
Remove leaves from the remaining thyme, and finely slice remaining sage. Melt 1 tablespoons of butter In a large skillet over medium high heat. Add leeks, thyme leaves, and sliced sage. Cook, stirring often, until the leeks are softened but not browned, about 4 minutes. Combine leeks and chicken.
Melt remaining butter in the skillet over medium high heat and add flour. Cook, stirring often, until flour just begins to brown, about 2 minutes. Whisking constantly, slowly add 1 1/2 cups reserved cooking liquid and Dijon mustard and bring to a simmer. Remove from heat and whisk in cream, then season to taste with salt and pepper. Pour sauce over chicken and leeks and mix until fully incorporated; taste and season again with salt and pepper if necessary. Allow the mixture to fully cool before assembling pie.
To assemble the pie: Adjust the oven rack to middle position and preheat to 400°F. Divide puff pastry into 2 pieces and roll each piece into a 9- by 11-inch rectangle. Place 1 rectangle on a lined baking sheet, then place the filling in the center of the pie leaving a 1 inch border. Brush the border with beaten egg, then place the remaining sheet of pastry on top. Pinch the edges closed, then brush the edges with egg and fold each edge over. Brush the rest of the pie with egg. With the tip of a knife, make two holes for the center for the steam to escape, Gently score the top of the pie. Bake until pie is golden brown and crisp, about 20 minutes. Transfer to a serving platter and serve.