There are about 15 species of walnut and many varieties within these groups. Next to the almond, walnuts are the most popular nut in Europe.

Green walnuts are picked before the shell has formed. They're normally immersed in brine until they become dark green, before they're dried and pickled. They're traditionally served as an accompaniment to cheese or cold meats.

Half-ripe walnuts are often sold preserved in syrup.

Shelled, dried walnuts have a short life of around 2-3 months. Keep them dry in an airtight container inside the fridge or freezer to prolong freshness.

In the kitchen
The most common variety of walnuts used in Europe are the dried ripe ones. Still in their shell, they're sometimes served as a special course at the end of a meal, or with cheese.

Half or whole nuts are often used as a decoration for desserts, while chopped ones add texture and flavour to puddings, ices and an array of sweet dishes - pastry, biscuits, pies and more.

In savoury cooking, walnuts are often ground to make creamy soups, and are tasteful additions to sauces and stuffings - especially good when paired with poultry and oily fish.

Walnuts add crunch to salads, working well with carrots, apples, celery.

Walnut oil has a delicate flavour, often used in dressings, or to sprinkle over cooked pasta. A dash of walnut oil added to dishes which already contain walnuts accentuates their natural flavour.

Did you know
The Greeks and Romans believed that walnuts, and their resemblance to the human brain, were good for curing headaches