The hazelnut's strong, distinctive flavour makes it popular with chefs. What is it? The nut of the hazel tree. It's covered in a smooth, shiny brown shell that's fairly easy to crack. What to look for: freshness. If the nuts are sold in packets, you can't tell how fresh they are (other than by checking the expiry date) and if they've been stored correctly (in a cool environment). Once the package is open, smell them to make sure they're not rancid. If buying nuts in the shell, examine them for wormholes. How are they available? The nuts are sold whole (in and out of the shell, and with or without the skin - the latter is usually referred to as 'blanched'), chopped and ground. They are best stored whole because the oils begin to break down the more they're processed. Hazelnuts are pressed for oil, ground for hazelnut butter and made into liqueurs such as Frangelico. They're often cooked with caramelised sugar to make praline (not to be confused with the pecan and brown sugar confection made in New Orleans); praline can be ground in a food processor to a rough powder and used to decorate cakes or flavour ice creams. Heavy-duty commercial rollers are needed to make thick, smooth praline paste. If this mixture is combined with chocolate it becomes gianduja, of which Nutella is one example. How to store: hazelnuts should be stored in the fridge or freezer. What else? The best flavour of the nuts isn't revealed until they've been toasted and the thin, bitter skin removed. Toast them in the oven until they're fragrant and the skins begin to crack and pull away from the nuts. Rub them between your hands to loosen the skins then pick out the nuts, leaving behind as much of the skin as possible (a little skin attached is OK). How to use: in desserts, such as the recipes (left). In culinary terms, when butter is melted and cooked until it takes on a rich, brown colour with a nutty smell, it's known as beurre noisette, or hazelnut butter. This is delicious mixed with capers and served over grilled fish and fried calves' brains or other organs, then sprinkled with chopped, toasted hazelnuts to enhance the nuttiness. Vinaigrettes have an entirely different flavour when made with hazelnut oil instead of extra virgin olive oil.