Ingredient

Walnuts

Walnuts are the most temperamental nut in a kitchen. They are high in polyunsaturated oil, which means they go rancid faster than almost any other nut, and their skins are tannic, which means they can taste bitter even when perfectly fresh. Both problems have straightforward answers.

Rancidity is the main problem

Walnut oil is highly unsaturated, and unsaturated fats oxidise readily when exposed to air, warmth and light. A rancid walnut tastes bitter, sharp, and faintly of paint or crayons — and because the change is gradual, people frequently eat rancid walnuts without identifying what is wrong, and conclude they simply do not like walnuts.

Taste one before you use them. A fresh walnut is sweet, buttery and mild with a slight tannic edge. If it tastes sharp, bitter or waxy, the batch is stale, and nothing you do to it in a recipe will fix that.

Store them cold. The fridge is good and the freezer is better. Walnuts kept in a warm cupboard for six months are almost certainly past it, and buying them in small quantities from somewhere with turnover is worth more than any storage technique.

Whole walnuts in their shells keep considerably longer than shelled halves, because the shell excludes air.

The other bitterness — the skin

Even a fresh walnut carries tannins in its papery brown skin, and those are genuinely bitter and astringent. In some dishes that is welcome; in others it fights everything.

Toasting reduces it markedly. Ten minutes in a moderate oven, or a few minutes in a dry pan, until they smell nutty and the skins darken slightly. Toasting also drives off moisture and deepens the flavour, and toasted walnuts are better than raw ones in more or less every application.

Rubbing the skins off after toasting — in a clean tea towel, while still warm — removes more of it again. Worth doing for a delicate dessert or a smooth sauce; not worth the effort for a salad.

Blanching in boiling water for a minute is the thorough method, used where the walnut needs to be pale and completely un-bitter, as in some Middle Eastern sauces.

What to do with them

• In a salad, toasted, with a sharp dressing, blue cheese, pear or apple, and bitter leaves. The classic combination and it works because everything in it answers the walnut.
• Muhammara — the Syrian roasted pepper and walnut dip, with pomegranate molasses. One of the great walnut dishes.
• Fesenjan — the Persian stew of ground walnuts and pomegranate, cooked long until the oil separates. Extraordinary and unlike anything else.
• Baklava and Middle Eastern pastries, where walnut is as traditional as pistachio.
• In a pesto, in place of pine nuts, which is cheaper and arguably better.
• In bread, particularly with rye and with cheese.
• Candied, with sugar and salt, for a salad or a cheeseboard.
• Pickled walnuts — green unripe walnuts pickled whole in spiced vinegar. Intensely British, intensely divisive, and excellent with cold meat and cheese.

Buying and keeping

Colour

Pale golden-brown kernels. Very dark, shrivelled or oily-looking halves are old.

Smell

Sweet and mildly nutty. Sharp, paint-like or bitter means rancid.

Form

Halves keep better than pieces, which have more cut surface exposed to air. Whole in-shell keeps longest.

Storage

Airtight in the fridge for months, or the freezer for a year. Not a warm cupboard.

Allergen

Walnuts are tree nuts, one of the fourteen allergens that must be declared in food sold in the UK.

Black walnut

A different American species, much stronger, more assertive and slightly medicinal. Not interchangeable with the common English walnut.

Common questions