Leek
Leeks give a mild onion-like flavor, adding sweetness and aroma to dishes.
Leeks are a long, mild member of the onion family, grown around the Mediterranean since ancient times. Instead of forming a bulb, they make a thick stalk of tightly wrapped leaves that tastes gently oniony, sweet and a little grassy.
Cooks love them for their soft, silky sweetness. Sweated in butter, they melt into the base of soups, gratins, risottos and tarts, and they are the other half of the famous potato-leek soup.
Flavor profile
Aroma: oniony, mild
Good to know
Origin: Mediterranean
Forms: whole
Season: Leeks are hardy and at their best from autumn through early spring, but they are available year-round.
Nutrition: A mild allium that adds fibre and flavour to soups and sides.
Storage: Keep leeks unwashed and untrimmed in a loose bag in the fridge crisper for 1–2 weeks. Store them away from mushrooms, apples and other foods that soak up smells. Slimy outer layers can be peeled off, but a soft, mushy stalk or a sour smell means it is past its best. To freeze, slice and wash, blanch for 1 minute (or skip it for soups), dry and freeze flat for up to 10 months; use frozen leeks only in cooked dishes.
How to use leek
Soup Foundations
Sweat leeks in butter to break down fructans, adding sweetness to soups.
Roasting Companion
Roast leeks for the Maillard reaction, caramelizing sugars and deepening flavor.
The science of leek
- Leeks contain the same sulphur compounds as onions, but in lower amounts, so they taste mellow rather than sharp. Gentle cooking turns those compounds sweeter and softer.
- Leeks store some of their energy as fructans, chains of fructose. Long, gentle cooking breaks some of those chains down, adding to the natural sweetness of sweated or braised leeks.
- Because the stalk grows up through soil that is piled around it to keep it pale, grit gets trapped between the layers. Slicing first and then washing is the only reliable way to remove it.
- Roasting or charring leeks at high heat drives off water and triggers the Maillard reaction, giving browned, nutty, almost caramelised edges with a meltingly soft centre.
How to choose leek
Choose firm, straight leeks with a long white and pale green section and crisp, dark green tops. Medium leeks, around 2–4 cm thick, are more tender than giants. Avoid any with yellowing, slimy or dried-out leaves, or a bulbous base, which can mean a tough core.
Substitutes for leek
| Swap | Amount | What changes |
|---|---|---|
| Onion | use about 1 medium onion per large leek | Stronger and sharper; cook it slowly to bring out sweetness. |
| Shallot | about 2–3 shallots per leek | Mild and sweet like leek, with a slight garlicky edge. |
| Scallion (spring onion) | 1:1 by volume | Fresher and grassier; add later in cooking or use raw. |
| Fennel bulb | 1:1 | Sweet and soft when sweated, with a gentle aniseed note. |
What goes with leek
- Potato. Leeks and potato are the classic soup pair, sweet allium and soft starch.
- Butter. Butterfat softens leek's sharpness, lending a smooth mouthfeel.
- Bacon. Bacon's fat and smoke amplify leek's sweet, oniony flavor.
- Chicken Stock. Leek's mild sweetness deepens chicken stock's savory flavor.
- Mushroom. Sweet leeks balance mushroom's earthy depth.
- Salmon. Leeks' mild sweetness suits salmon's rich flesh.
- White Wine. White wine's acid lifts leek's mild sweetness in braises.
- Parmesan. Parmesan's salty umami deepens leek's gentle sweetness.
- Thyme. Thyme's earthy aroma boosts leek's mild sweetness.
Mistakes to avoid
- Inadequate cleaning leaves grit.
- Overcooking makes them mushy.
Ideas for tonight
- Make potato-leek soup.
- Sauté with garlic as a side.
- Add to a vegetable tart.
Leek: questions
What part of the leek do you eat?
The white and pale green parts are tender and used in most recipes. The dark green tops are tougher but great for flavouring stocks and soups.
How do you clean leeks?
Trim the root and dark tops, slice the leek lengthways or into rings, then swish the pieces in a big bowl of cold water. Grit sinks, so lift the leeks out rather than pouring them into a colander.
Can you eat raw leeks?
Yes, but they are firmer and more pungent than cooked leeks. Slice very thinly and use sparingly in salads, or quick-pickle them.
Can you freeze leeks?
Yes. Slice, wash and dry them, then freeze flat in a bag. They go soft when thawed, so use them in soups, stews and gratins.
How do you know when leeks are cooked?
Sweated leeks are done when they are soft, silky and translucent, usually 8–12 minutes over low heat. Avoid browning them if you want a sweet, gentle flavour.
Are leeks and green onions the same?
No, though they are cousins. Leeks are much larger, thicker and milder when cooked; green onions are thin, fresher and often eaten raw.
What does leek taste like?
Leeks give a mild onion-like flavor, adding sweetness and aroma to dishes., with an aroma that is oniony, mild.
What goes well with leek?
Leek pairs best with potato, butter, bacon, chicken stock, mushroom. Leeks and potato are the classic soup pair, sweet allium and soft starch.
How do you use leek in cooking?
Soup Foundations: sweat leeks in butter to break down fructans, adding sweetness to soups.
How should you store leek?
Store in the refrigerator, unwashed and untrimmed.
What is the most common mistake with leek?
Inadequate cleaning leaves grit.
Onion
Shallot
Scallion
Potato
Butter
Mushroom
Chicken Stock
Bacon