Leftover Chicken, Leek and Mushroom Pie

Leftover chicken, leek and mushroom pie turns cooked chicken into a creamy, savory filling under crisp golden pastry. Leeks bring gentle sweetness, mushrooms add depth, and using already-cooked chicken makes this a practical way to build a satisfying dinner without overcooking the meat.

Ingredients

2 tablespoons (28 g) unsalted butter
1 tablespoon (15 ml) olive oil
1 large leek, about 1½ cups (200 g) sliced white and pale-green parts
8 ounces (225 g) cremini or button mushrooms, sliced
2 tablespoons (16 g) all-purpose flour
1 cup (240 ml) chicken stock, preferably low-sodium
½ cup (120 ml) whole milk or heavy cream
1 teaspoon (5 ml) Dijon mustard
½ teaspoon dried thyme, or 1 teaspoon (1 g) fresh thyme leaves
½ teaspoon fine salt, plus more to taste
¼ teaspoon black pepper
3 cups (420 g) cooked chicken, skin removed and cut or shredded into bite-size pieces
1 cup (120 g) frozen peas, thawed
1 sheet (about 250 g) ready-rolled puff pastry, thawed according to package directions
1 large egg (about 50 g), beaten with 1 teaspoon (5 ml) water, for the pastry wash

Instructions

Heat the oven to 400°F (200°C). Set a rack in the middle. If your cooked chicken has been refrigerated, keep it chilled while preparing the filling. Use a 9-inch (23 cm) deep pie dish or a similar 1½-quart (1.4-liter) ovenproof dish.
Trim the leek, slice it lengthwise, and rinse between the layers to remove grit. Slice it thinly. Heat the butter and oil in a large skillet over medium heat. Add the leek and cook for 5 minutes, stirring occasionally, until softened but not browned.
Add the mushrooms and cook for 6–8 minutes, stirring now and then, until their released liquid has mostly evaporated and the slices begin to brown. This step helps keep the filling from becoming watery.
Sprinkle in the flour and stir for 1 minute to coat the vegetables. Gradually pour in the stock, stirring to smooth out any lumps, then add the milk or cream, mustard, thyme, salt, and pepper. Bring to a gentle simmer and cook for 3–4 minutes, stirring, until the sauce thickens enough to coat the back of a spoon. Take the pan off the heat.
Fold in the cooked chicken and peas. Spoon the filling into the pie dish and spread it evenly. Let it cool for about 10 minutes so the pastry is less likely to soften on contact. If the filling is piping hot, allow a little longer; it should not sit at room temperature for more than 2 hours in total.
Lay the pastry over the filling. Trim the edges, leaving a small overhang, and press the pastry against the rim of the dish to seal. Cut a small slit in the center to let steam escape. Brush the top with beaten egg, avoiding a puddle of egg around the edge.
Bake for 25–30 minutes, until the pastry is puffed and deeply golden and the filling is bubbling at the vent or edges. Because this pie uses cooked chicken, the pastry and filling need to be thoroughly hot; check the center with a food thermometer. USDA FSIS advises reheating leftovers to a safe minimum of 165°F (74°C).
Rest the pie for 10 minutes before serving. The filling will settle slightly and be easier to portion. If the pastry browns before the center is hot, cover it loosely with foil and continue baking until the center reaches 165°F (74°C).

Tips

Wash leeks carefully: grit hides between the layers. Slice first, then rinse in a bowl of cold water and lift the pieces out, leaving sediment behind.
Keep the filling thick. Let the mushrooms release and cook off their liquid, and simmer the sauce until it coats a spoon. If it still seems loose, simmer another minute before adding the chicken.
Use chicken that was refrigerated promptly and is within its safe storage window. Avoid leaving cooked chicken or the finished filling at room temperature for more than 2 hours (1 hour if the room is above 90°F/32°C).
No puff pastry? Use shortcrust pastry for a more traditional, less flaky top, or make individual pies in ovenproof dishes. Adjust baking time until the tops are golden and the centers reach 165°F (74°C).

Serving Suggestions

Serve the pie hot with a crisp green salad dressed with vinaigrette to balance its creamy filling. Steamed green beans, broccoli, or roasted carrots also make easy sides. The pie is substantial, so a simple vegetable accompaniment is usually enough; spoon any sauce from the dish over each portion.

Variations

For a richer filling, use heavy cream in place of milk; for a lighter one, use milk and keep the butter amount as written. Add ½ cup (60 g) diced carrot or celery with the leek, allowing them to soften before adding the mushrooms. A handful of chopped parsley stirred in at the end adds freshness.

You can replace the peas with 1 cup (120 g) of chopped cooked green beans or omit them. For a stronger mushroom flavor, use a mix of cremini and shiitake mushrooms, but remove tough shiitake stems. If the chicken is already well seasoned, reduce the added salt and taste the sauce before assembling.

Storage and Reheating

Refrigerate leftover pie within 2 hours of baking, in a covered container or tightly wrapped, and eat within 3–4 days. For the best pastry texture, reheat portions in a 350°F (175°C) oven until the center reaches 165°F (74°C), usually 20–30 minutes from chilled depending on portion size. Cover loosely with foil if the pastry is browning too quickly. A microwave also works for an individual portion; heat in short intervals and check that it reaches 165°F (74°C).

To freeze, cool the pie promptly, wrap it well, and freeze for up to 2 months for best quality. Thaw overnight in the refrigerator, then reheat until the center is 165°F (74°C). Avoid reheating the same portion more than once.

Frequently Asked Questions

Can I make this pie with raw chicken?
Yes, but cook the chicken separately before adding it to the filling, then check it with a food thermometer to confirm it reaches 165°F (74°C). This recipe is designed for cooked leftover chicken, so adding raw chicken directly can leave the filling undercooked and watery.

Can I make the filling ahead?
Yes. Make the filling, cool it promptly, and refrigerate it in a covered container for up to 3–4 days. Assemble with pastry shortly before baking. If baking from a cold filling, allow extra time and check that the center reaches 165°F (74°C).

Why is my pie filling runny?
The mushrooms may not have cooked off enough liquid, or the sauce may not have simmered long enough to thicken. Next time, cook the mushrooms until their liquid evaporates and simmer the flour-and-stock sauce until it coats a spoon before adding chicken and peas.

Can I use a pastry lid without a bottom crust?
Yes. This recipe is made with a pastry lid only, which keeps the pie straightforward and helps avoid a soggy base. If you add a bottom crust, use a deep dish and consider blind-baking the base according to its package directions before adding the filling.

What cooked chicken works best?
Any plain cooked chicken works, including roasted, poached, or rotisserie chicken. Remove bones and skin, and cut or shred it into bite-size pieces. If it is strongly seasoned, taste the sauce before adding extra salt.

Can I bake the pie from frozen?
For even heating, thaw it overnight in the refrigerator before baking or reheating. Baking a fully assembled frozen pie can brown the pastry before the center is hot enough; if you do bake it frozen, use a thermometer and continue until the center reaches 165°F (74°C).

More recipes to cook

Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

Spotted an error? Tell us and we will correct it (corrections policy).