3 1/2 pounds skinless, boneless chicken thighs
1 pound wild mushrooms or 1 1/2 ounces dried wild mushrooms
2 cups chicken stock
2 to 3 tablespoons butter
1 large onion, chopped
2 carrots halved lengthwise and cut crosswise 1/4-inch thick
1 cup fresh or frozen peas
1 tablespoon unbleached all-pupose flour
1 cup heavy cream
1/2 cup dry sherry
1 tablespoon chopped fresh flat-leaf parsley
1 tablespoon chopped fresh thyme
Salt and freshly ground black pepper
Potpie Pastry, rolled out
1 egg white, beaten
1. Preheat the oven to 375 degrees F.
2. In a large saucepan, simmer the chicken thighs in water to cover until almost cooked through, about 20 minutes. Let cool, then pull into large pieces.
3. If using dried mushrooms, place in a bowl and cover with boiling water; let soak for 30 minutes. Strain the mushroom liquid through a piece of doubled cheesecloth to avoid grit, reserving the mushroom stock. Do not waste this mushroom elixir. Measure the mushroom stock and add enough chicken stock to make up to 2 cups. In a medium saucepan, bring the 2 cups of chicken stock (or mushroom-chicken stock) to a boil and cook until reduced to 1 cup. In a large skillet, melt 2 tablespoons butter until foaming. Add the onion, carrots, and peas (if using fresh) and sauté over medium-low heat. Cover the vegetables and sweat until the onion is softened, about 10 minutes. In a large saucepan, sauté the mushrooms (if using) in 1 tablespoon butter, until mushrooms have released all of their liquid and browned slightly. Add to the vegetables. Add the flour to the vegetables and cook until evenly coated.
4. Slowly stir in the reduced stock and bring to a simmer, until the mixture begins to thicken, about 5 minutes. Stir in the cream and sherry, then fold in the parsley and thyme. Return to a gentle simmer and cook for 5 minutes. Add the chicken and frozen peas (if using); season with salt and pepper. (The mixture can be refrigerated at this point for up to 24 hours). Divide the chicken mixture among four ramekins or spread in one large baking dish. If using individual ramekins, cut out 4 disks of the Potpie Pastry, using an overturned ramekin as your guide; place one disk on top of each ramekin. If using a single baking dish, flip the silicone sheet of Potpie Pastry onto the baking dish; remove the silicone.
5. Press the pastry slightly to the baking dish(es) to adhere. Brush the top of the pastry with the egg white.
6. Bake the pie(s) for 45 minutes. Let cool slightly.