NST kitchen · dinner
Creamy leek and mushroom pie
Soft leeks and browned mushrooms in a creamy mustard sauce, covered with a golden puff-pastry lid.
- vegetarian
- Prep (est.)
- 20 min
- Cook (est.)
- 55 min
- Total (est.)
- 85 min
- Base servings
- 4
Total includes 10 minutes waiting time.
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Ingredients
One fixed batch makes 4 servings. Keep the listed quantities, pan and method unchanged. For more, repeat the full batch; for fewer, follow the recipe's storage guidance for unused portions.
Ingredients for 4 servings.
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You will need
- Oven, hob and deep frying pan
- Deep ovenproof pie dish about 24 cm wide, at least 6 cm deep and 2.5 litres capacity; baking tray and oven gloves
- Knife, board, scales, jug, wooden spoon and pastry brush
- Refrigerator for keeping pastry chilled
Let's make it
The method
0 of 5 steps marked
Keep your place for this page visit. Ticks do not confirm doneness or food safety; follow every cooking and storage instruction.
Step 1. Soften and brown
Heat the oven to 180°C fan / 200°C conventional and leave the pastry refrigerated. Melt the butter in the deep pan over medium heat. Add leeks and cook for 6–8 minutes until soft. Add mushrooms and thyme, turn the heat up slightly and cook for about 8–10 minutes, stirring, until their released liquid has mostly evaporated. Add garlic for the final minute.
Step 2. Make a smooth filling
Stir the flour through the vegetables for 1 minute without letting it burn. Gradually stir in the filling milk, then the stock and mustard. Bring to a gentle simmer and cook for 3–4 minutes, stirring, until the sauce thickly coats the vegetables with no dry flour pockets. It should not be a loose soup.
Step 3. Fit the pastry lid
Spoon all the filling into the deep 2.5 litre pie dish, leaving at least 2 cm below the rim. If that clearance is unavailable, transfer all the filling to a suitable deeper ovenproof dish that the pastry sheet can still cover; do not discard filling or force it beneath the lid. Let heavy steam subside for about 5 minutes; do not leave it to stand for a later meal. Unroll the pastry, lay it over the dish without stretching, trim any excess and press the edge to the rim. Cut two small steam slits in the centre and brush the top with the separate brushing milk.
Step 4. Bake
Put the dish on a baking tray. Bake immediately for roughly 30 minutes, following any longer pastry-pack requirement, until risen and golden and the pastry is cooked rather than doughy underneath. Check through a slit that the filling is steaming hot in the centre; a golden lid alone does not confirm a hot filling. Cover loose edges with foil only if they brown too quickly.
Step 5. Stand and portion
Lift onto a heatproof surface using oven gloves and stand for about 5 minutes. Divide the lid and filling into four portions. Take care with escaping steam and serve promptly.
Make it work for you
Swaps & variations
- Use ordinary closed-cup mushrooms instead of chestnut mushrooms in the same weight.
- Replace Dijon with 10 g wholegrain mustard for a different texture; both contain mustard. Choose vegetarian-labelled pastry and stock for the stated vegetarian dish.
Recipe notes & sources
Sources support the points stated below; they are not evidence that NST has cooked or tested this recipe.
- FSA cooking guidance
Cooking endpoints, clean temperature probes and once-only reheating; not validation of these recipes, estimated times or flavours.
Checked 2026-10-23 - FSA chilling and defrosting guidance
Prompt cooling, chilled leftovers and label-led storage; no shelf-life experiment has been conducted by NST.
Checked 2026-10-23 - FSA allergen advice for consumers
Ingredient and precautionary-label checks, including the distinction between vegan and allergen-free; no product certified.
Checked 2026-10-23
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About this serving photograph
Serving example photographed by Elaine Reg, not an NST kitchen-test photograph. The exact cheeses, recipe, quantities, pan and method may differ. Background wine and other dishes are not included. Proportionally resized and converted to WebP; no food or scene edits.
Soft potato gnocchi in a garlic and tomato sauce, finished with melted mozzarella and basil. Boil the gnocchi first, then give the hot sauce and cheese a short oven finish for a comforting dish to share.