Black Truffle

How to recognise it

This truffle is a round, lumpy tuber that grows underground. It ranges from walnut to fist size. The black skin is reddish when young and covered in small, hard, many-sided warts. Cut it in half. Ripe flesh is purplish-black, marbled with fine white veins that turn reddish-brown in the air. It smells strong and earthy. Earthballs (Scleroderma) are poisonous. They have a thick, yellowish to brown, scaly skin and smell of gas. Inside they are firm and dark. The winter truffle (Tuber brumale) and the imported Chinese truffle (Tuber indicum) look similar. But they are worth far less.

Where it grows

It grows underground among the roots of oaks (above all holm and downy oak) and of hazel. It needs well-drained, lime-rich soil in sunny hill country. A patch of bare, burnt-looking ground around a tree often shows where it grows. It is native to southern France, eastern Spain and central Italy. Much of the crop now comes from planted truffle orchards.

When

It ripens in winter, from December to March. Markets peak in January. Storms in late July and August, while it swells, decide the size of the crop.

Picking

You find it with a trained dog. Dig only where the dog marks, with a small truffle spade. Take only ripe truffles and fill the hole again. Truffle hunting is regulated. Italy requires a licence after an exam and its regions set the seasons. Spanish regions set seasons and permits. In France truffles belong to the landowner. In Germany wild truffles are protected. Check the local rules before you look.

Cooking

If you're certain of the identification, brush it clean under cold water just before use. Shave or grate it raw over warm dishes. Or warm it gently in fat, with eggs, butter, pasta, risotto or potatoes. Long cooking kills the aroma.

Keeping

Wrap it in kitchen paper in a closed jar in the fridge. Change the paper daily and use it within days, as the aroma fades. Eggs kept in the jar take on its scent. Freezing keeps the aroma better than drying.

Toxic look-alikes

• Scleroderma citrinum · Toxic - do not eat
• Scleroderma polyrhizum · Toxic - do not eat
• Scleroderma areolatum · Toxic - do not eat
• Scleroderma verrucosum · Toxic - do not eat
• Scleroderma cepa · Toxic - do not eat