Leeks

Store unwashed in a plastic bag in the crisper drawer. Blanch and cool before freezing for best quality. Trim dark-green tops before storing to extend freshness.

Clean thoroughly between layers by slicing lengthwise and rinsing under running water—soil hides in the white and light-green sections.

Use both the white/light-green parts and dark-green tops: the white part is tender for eating, dark leaves add flavor to stocks and soups.

Cook gently and low-and-slow to bring out natural sweetness; high heat can make them tough and bitter.

Leeks shrink significantly when cooked—one large leek becomes quite small, so don't be shy with quantity.

Cream, butter, and cheese (classic in soups and gratins)

Potatoes, carrots, and celery (mirepoix-style combinations)

Fresh herbs: thyme, tarragon, parsley, chives

White wine and chicken or vegetable stock

Mustard and lemon

Not cleaning properly—grit between layers ruins the dish.

Cooking at too-high heat, which toughens and dries them out.

Discarding the dark-green tops, which are flavorful in stocks and soups.

Crowding the pan during cooking, which prevents caramelization and even cooking.