Chicken, Leek & Mushroom Pie with Flaky Lattice Top

A golden, buttery lattice-topped pie packed with tender chicken, silky leeks and mushrooms in a creamy, savoury sauce—all baked in a proper pastry base (not a pot pie).

Ingredients

• 2 sheets frozen puff pastry, thawed (about 320–375g each), divided (1 for base, 1 for lattice top)
• 700g boneless skinless chicken thighs or breast, cut into 2.5cm / 1-inch pieces
• 2 large leeks, white + pale green parts only, halved lengthwise then sliced (about 400g prepared)
• 300g mushrooms (cremini/button), sliced
• 2 cloves garlic, finely minced (pantry staple)
• 60g / 4 tbsp butter, divided
• 3 tbsp olive oil, divided (pantry staple)
• 1/3 cup (50g) plain flour (all-purpose)
• 2 cups (500ml) chicken stock (pantry staple if using bouillon)
• 1 cup (250ml) milk (or more stock if preferred)
• 1 tsp Dijon mustard (optional but excellent; pantry staple)
• 1 tsp dried thyme (or 1 tbsp fresh, chopped; pantry staple)
• 1/2 tsp black pepper (pantry staple)
• 1 1/2 tsp salt, to taste (pantry staple)
• 1/2 cup (60g) frozen peas (optional; pantry staple/freezer staple)
• 1 egg, beaten with 1 tbsp water (egg wash)
• 1 tbsp sesame seeds or flaky salt (optional, for finishing; pantry staple)

Method

• 1

  Step 1: Prep the pan + pastry base

  Heat oven to **200°C / 390°F (180°C fan)**. Lightly grease a **23cm / 9-inch deep pie dish** (or similar, about 5cm/2-inch deep).

• 2

  Step 2: Brown the chicken

  In a large, deep skillet over **high heat**, add **1 tbsp olive oil** and **20g (1 1/2 tbsp) butter**. Add chicken, **season with 1/2 tsp salt + 1/4 tsp pepper**, and sear until lightly golden on the outside (it doesn’t need to be cooked through), **about 4–5 minutes**. Remove to a bowl.

• 3

  Step 3: Cook leeks + mushrooms (build flavour)

  Reduce heat to **medium-high**. Add **1 tbsp olive oil** plus **20g (1 1/2 tbsp) butter**.

• 4

  Step 4: Make the creamy sauce

  Sprinkle over **flour** and stir constantly for **1 minute** (it should look pasty and coat the veg).

• 5

  Step 5: Finish filling + cool slightly

  Return chicken (and any juices) to the pan. Simmer gently until chicken is just cooked through and sauce is thick and creamy, **4–6 minutes**. Stir in peas (if using).

• 6

  Step 6: Blind bake the pastry base (key for a crisp bottom)

  Line the chilled pastry base with baking paper and fill with **pie weights/dried beans/rice**. Bake **15 minutes**. Remove weights/paper, then bake **5 minutes** more until the base looks dry and just starting to turn golden at the edges.

• 7

  Step 7: Fill the pie

  Spoon the chicken-leek-mushroom filling into the warm pre-baked shell and level the top.

• 8

  Step 8: Make the lattice top

  Use the **second puff pastry sheet**. Cut into **12–14 strips** about **2cm / 3/4-inch** wide (a pizza cutter works well).

• 9

  Step 9: Egg wash + bake until deeply golden and flaky

  Brush lattice and edges with **egg wash** (avoid letting it pool in the gaps or it can “glue” the lattice shut). Sprinkle with sesame seeds or flaky salt if you like.

• 10

  Step 10: Rest (so it slices cleanly)

  Rest **15 minutes** before slicing. This lets the sauce set so you get proper wedges, not a puddle.

Tips

• **Preventing a soggy bottom:** Blind baking is the big one. Also, make sure the filling is **thick** (should mound slightly on a spoon, not run like soup).
• **Chicken thighs vs breast:** Thighs stay juicier and reheat better; breast is leaner—either works.
• **Make-ahead:** Cook filling up to **2 days ahead** and refrigerate. Assemble and bake when ready (add **5–10 minutes** bake time if the filling is fridge-cold).
• **Freezing:** Freeze the fully baked pie (cooled) wrapped well for up to **2 months**. Reheat from thawed at **180°C / 350°F** for **20–25 minutes** until hot.
• **Serve with:** Steamed greens, buttery peas, or a simple side salad; for a heartier plate, add mashed potatoes.

Nutrition (per serving, estimate)