Leek and Potato Soup
Sweat the leeks in butter with a lid on and do not let them colour. Browned leeks make a grey soup, and this one is supposed to be pale green.
- Prep
- 15 min
- Cook
- 35 min
- Total
- 50 min
- Serves
- 4
- Revisions
- 1
Allergens
- Celery
- Milk
- Sulphites
Named from the ingredients as written, including those carried in from sub-recipes. This is not a guarantee — check the labels on what you actually buy, and note that a product’s recipe can change.
Ingredients
Serves
Soup
To finish
Method
Soup
Slice the leeks and wash them thoroughly in a bowl of cold water, lifting them out rather than pouring, so the grit stays behind.
Melt the butter in a heavy pan over low heat, add the leeks and the salt and put a lid on.
Sweat for 15 minutes, stirring occasionally, until completely soft and collapsed with no colour on them at all.
The lid and the low heat are the recipe. Leeks that brown make a grey-brown soup with a caramelised flavour, which is a perfectly good soup and is not this one — this is supposed to be pale, sweet and clean.
Add the potatoes, stock and bay leaf and bring to a simmer.
Cook uncovered for 18 to 20 minutes, until the potato falls apart under a spoon.
Fish out the bay leaf and blend until smooth, working in batches with the jug no more than two-thirds full.
Do not blend it for longer than it needs. Potato starch turns gluey when it is overworked, and thirty seconds too long in a powerful blender gives you wallpaper paste.
To finish
Return to the pan, stir in the cream and the white pepper and warm through without boiling.
Taste for salt — it will need more than expected — and serve with chives over the top.
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What to expect
- Taste
Sweet, mild and buttery, with the leek clearly identifiable rather than buried. It is a quiet soup and its virtue is that it tastes precisely of two things.
- Aroma
Butter and sweet allium. Gentle.
- Texture
Velvety. The only failure mode is gluey, which comes from over-blending potato starch.
- Sound
None.
- How the flavour moves
Butter first, then sweetness, then a long mild finish. White pepper arrives right at the end.
- Serve it
Hot, or properly chilled as vichyssoise. Lukewarm is the worst version.
- Goes with
Good bread and butter. It does not want anything else.
Cook's notes
- Difficulty
Beginner.
- Cost
Very low.
- Equipment
A heavy pan with a lid and a blender.
- When to make it
Autumn and winter, and any time there are leeks to use.
- Best season
Leeks are a winter vegetable and this is a winter soup.
- You know it is done when
The leeks should be completely collapsed and translucent with no golden edges anywhere. The finished soup should be pale ivory-green.
- And it feels like
Smooth and pourable, thick enough to coat a spoon.
- Food safety
Nothing unusual. Blending hot liquid is the one hazard — fill the jug no more than two-thirds and hold the lid down with a cloth, or use a stick blender in the pan.
- Where it goes wrong
- Browning the leeks, which changes the soup entirely.
- Not washing them properly, which cannot be fixed later.
- Waxy potatoes, which do not break down and leave it thin.
- Over-blending, which makes potato starch gluey.
- Using the dark green tops, which turn it khaki.
- Under-salting — a smooth soup needs more salt than a chunky one to taste seasoned.
- If it does go wrong
Gluey: over-blended, and there is no fix. Thin: simmer uncovered to reduce, or add another boiled potato. Grey: the leeks browned. Gritty: it was not washed, and straining will not fully save it. Bland: salt, then white pepper, then a squeeze of lemon.
- Making it ahead
Better the next day. Make it ahead and add the cream on reheating.
- Keeping it
Three days in the fridge.
- Reheating
Gently, without boiling.
- Freezing
Freezes for three months, best done before the cream goes in — dairy can go grainy on thawing.
- Leftovers
Chilled and thinned with a little more cream, it is essentially vichyssoise.
- Scaling it
Doubles cleanly.
- Substitutions
Chicken stock makes it richer and stops it being vegetarian. The dark green tops of the leeks can go in, and they will turn the soup a dull khaki — keep them for stock instead.
- Dietary swaps
Contains milk from the butter and cream, plus celery and sulphites from shop-bought stock. Vegan with olive oil and a plant cream, and it works well. Gluten free, egg free and nut free.
- Shopping for it
Nothing unusual. Leeks are at their best from autumn through to early spring.
- Keeping the cost down
One of the cheapest meals in the collection. The dark leek tops make stock, so nothing is wasted.
- Sustainability
Vegetables, butter and stock, and one of the lowest-impact dishes here. Both main ingredients grow well in Britain and are in season through the winter, so this is a genuinely local soup for most of the year. Keeping the dark green tops for stock rather than binning them uses about a third more of each leek, which is the single most wasteful habit in this recipe as usually written.
- Nutrition
Mostly vegetables. The butter and cream are the fat and both can be reduced without ruining it.
- Worth it?
Keep the lid on and keep the heat down. Fifteen minutes of doing nothing is the entire recipe.
Where it comes from
- Origin
France, and Britain in parallel.
- Also called
Potage parmentier, or potage bonne femme.
- Said out loud
po-TAHZH par-mon-tee-AY.
- What the name means
Parmentier, after Antoine-Augustin Parmentier, the eighteenth-century French pharmacist and agronomist who campaigned to make the potato acceptable as human food in France, where it had been regarded as fit only for animals. Any French dish with 'parmentier' in the name contains potato because of him.
- History
Leek and potato soup is peasant cooking across northern Europe. Its best-known descendant is vichyssoise, created at the Ritz-Carlton in New York in 1917 by chef Louis Diat, who chilled the soup and enriched it with cream and named it after the spa town near his childhood home. It is therefore a French-American dish with a French name that is not eaten in France, which is an unusually tidy example of how these things happen.
- Why it matters
Domestic and unglamorous, and one of the first soups most people learn.
- When it is eaten
Cold weather, using up leeks, and feeding someone who is unwell.
- The traditional way
Sweating — cooking vegetables in fat under a lid so they soften in their own moisture without browning.
- How it changed
Blenders made it smooth. Before them it was a chunkier soup and arguably no worse.
- Regional variations
Vichyssoise, served cold. Scottish cock-a-leekie is a different soup with chicken and prunes.
- How this version differs
Nothing unorthodox. The instruction not to brown the leeks is given a reason, because it is the step that decides what the soup looks and tastes like and it is usually written as a bare instruction.
- Sources and credit
Louis Diat for vichyssoise; nobody for this.
Vegetable Stock
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French
British
Soups
Potatoes
Vegetarian