leeks
Also known as: leek
A member of the onion family shaped like an oversized green onion, with a milder, sweeter, more delicate flavor than a regular onion. The white and pale green part is what's usually cooked with (the dark green tops are tougher and more often used for stock); a classic base for potato-leek soup and similar creamy soups, where its subtlety lets the other ingredients lead.
Buying guidance
Choose leeks that are firm with crisp, unwilted green tops -- size doesn't affect flavor much, but very large leeks can have a tougher, more fibrous core that's worth trimming out.
Substitutions
- Onion, a milder variety like sweet onion or shallot -- more assertive flavor, but a reasonable substitute when leeks aren't on hand.
- Green onions (scallions), a larger quantity -- milder still, and adds less body to a soup than leeks do.
- Fennel -- a completely different flavor (aniseed) but a similarly delicate texture in a cooked dish.
Tips & common mistakes
Leeks grow partly underground and trap dirt and grit deep between their layers -- slicing them first, then rinsing the cut pieces thoroughly in a bowl of water (letting the grit sink to the bottom) removes it far more reliably than rinsing a whole leek under the tap.
Storage
Keeps refrigerated for one to two weeks, unwashed and untrimmed, wrapped loosely in a plastic bag -- trim and wash only right before using, since cut leeks dry out and spoil faster.