Flamiche aux Poireaux (Leek and Crème Fraîche Tart)

Flamiche aux poireaux belongs to the savoury tart tradition of northern France, where sweet, slowly softened leeks are enclosed in buttery pastry with a rich dairy custard. In this version, crème fraîche and eggs give the filling a smooth, gently tangy set, while Dijon mustard on the base, black pepper and a touch of nutmeg keep the flavour savoury rather than heavy. The tart should bake until lightly golden with a slight wobble in the centre, then rest so it slices cleanly. Served warm or at room temperature, it makes a satisfying vegetarian lunch with a green salad and is practical for preparing ahead.
Cuisine style Northern French savoury tart
Cooking style Make-ahead friendly • Crowd-friendly
Time commitment Make-ahead friendly

Why this recipe works

  • Classic leek filling: Gently cooking the leeks before baking brings out their sweetness and keeps the custard from tasting raw or watery.
  • Creamy set custard: Crème fraîche and eggs bake into a smooth, savoury filling with just enough tang to balance the buttery pastry.
  • Subtle seasoning: Dijon mustard, black pepper and nutmeg add depth without overpowering the delicate leek flavour.

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Timing notes

  • Chill the pastry: Chilling the dough and the lined tart case helps the pastry relax and hold its shape during baking.
  • Rest before slicing: Let the tart stand after baking so the custard settles and cuts more cleanly.
  • Serve warm or room temperature: The tart is at its most flexible when served warm or fully cooled to room temperature, making it useful for lunches and buffets.

Ingredient notes

  • Wash the leeks well: Slice the leeks before washing if they are sandy, then lift them from the water so any grit stays behind.
  • Use crème fraîche for tang: Crème fraîche gives the filling richness and a gentle acidity; Greek yoghurt makes a lighter, slightly sharper alternative.
  • Keep the nutmeg subtle: Nutmeg should sit in the background, adding warmth to the custard rather than becoming a dominant flavour.

Common mistakes

  • Do not overwork the pastry: Bring the dough together just until it holds; too much handling can make the baked case tough.
  • Avoid browning the leeks: Cook the leeks gently until soft and sweet. Browning changes the flavour and can make the filling taste harsh.
  • Do not overbake the custard: The centre should still have a slight wobble when the tart comes out of the oven; it will continue to settle as it rests.

Make-ahead tips

  • Prepare components ahead: The pastry and cooked leeks can be prepared in advance, then assembled with the custard before baking.
  • Reheat gently: Reheat slices in a 180°C (355°F) oven until piping hot, which helps the pastry stay crisper than microwaving.
  • Freeze baked slices: Cool the tart completely, wrap well and freeze. Defrost overnight in the fridge before reheating.

Equipment you'll need

Ingredients

Pastry

Filling

Instructions
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  1. Make the pastry: put the plain flour and fine sea salt in a bowl, then rub in the cold unsalted butter until it looks like fine crumbs. Add the cold water and bring together into a dough without overworking. Flatten into a disc and chill for 30 minutes.
  2. Meanwhile, prepare the leeks: trim, halve lengthways, then slice and wash well to remove any grit. Melt the unsalted butter in a frying pan over a medium-low heat, add the leeks and a pinch of the fine sea salt, and cook for 12 to 15 minutes until soft and sweet but not browned. Take off the heat and let cool slightly.
  3. Heat the oven to 190°C (375°F). Roll out the pastry on a lightly floured surface and line a tart pan, pressing it into the corners, then trim the edge. Chill the lined case for 10 minutes to help it hold its shape.
  4. Prick the base all over with a fork, then bake the tart case for 15 minutes until it looks dry and is just starting to colour. Remove from the oven and reduce the temperature to 180°C (355°F).
  5. Spread the dijon mustard in a thin layer over the warm tart base. In a bowl, whisk the eggs with the crème fraiche, black pepper, ground nutmeg, and the remaining fine sea salt. Stir in the softened leeks.
  6. Pour the filling into the tart case and bake at 180°C (355°F) for 25 to 30 minutes, until the custard is set with a slight wobble in the centre and the top is lightly golden. Rest for 10 minutes before slicing so the filling settles. Serve warm or at room temperature.

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Recipe notes

Serving suggestions

This recipe pairs well with:

A simple green salad

Tips

  • If your leeks are very sandy, slice them first, then swish in a bowl of cold water and lift out the clean leeks, leaving grit behind.
  • For neat slices, cool the tart for 20 minutes after baking, then cut with a sharp knife wiped clean between cuts.
  • Eggs should be thoroughly cooked for young children, older adults, and anyone who is pregnant or immunocompromised.

Substitutions

  • Replace Crème fraiche with Greek yogurt for a slightly tangier, lighter filling.
  • Replace Dijon mustard with whole-grain mustard for a milder heat and a coarser texture.

Storage

  • Refrigerate up to 3 days
  • Cool completely, then refrigerate in a sealed container. Reheat slices in a 180°C (355°F) oven for 10 to 12 minutes until piping hot, or eat at room temperature. Freeze well wrapped for up to 2 months and defrost overnight in the fridge before reheating.

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Recipe overview

  • Servings: 4 servings
  • Yield: leek and cream tart
  • Total time: 1h 35min (35min active)
  • Difficulty: Medium
  • Cuisine: French
  • Allergens:
    Eggs Gluten Milk Wheat
With serving suggestions Freezer friendly Kid friendly

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