As we drove through the mediaeval town of Pons, past its fast-flowing rivers and statuary commemorating the pilgrims who travelled through here on the way to Santiago de Compostela, a road-sign with 'Cognac' on it made an appearance. We were getting close at last. We'd come to Cognac to see the process that produces the drink of that name and lunch was to be at Hennessy's headquarters on the banks of the Charente River.

Lunch over, we were whisked to 'Le Peu', a distillery in the centre of the <it> Grande Champagne </it> which was busy distilling when we arrived. It's a famously oft-photographed room, the brass and copper pot-stills gleaming in the low winter sunlight. Each still is polished to a mirror finish, and the smell of the 'brouillis', the first pass through the still, hung heavily in the air. This is distilled a second time and results in an 'eau de vie' with a strength of about 70% alcohol by volume.

'Champagne' in the Charente region refers to land with a high content of chalk, where the best eaux de vie come from. In the area defined as 'Cognac' there is the Grande Champagne, the Petite Champagne, Borderies, Fin Bois, Bon Bois and Bois Ordinaires in descending order. Until the mid nineteenth century the rather sour white wines of Charente were distilled and sold as eau de vie. After 1860 these spirits from the region of Cognac began to be sold under that name.

At Hennessy's they consider all their spirits to be 'eaux de vie' until they have been blended and bottled at their chais, and then they are termed 'Cognac'. Each distilled wine from each grower is kept in barrel and aged, each barrel marked with the year, the grower, the provenance and the distillery. The barrels and the raw spirit form a perfect marriage, the Limousin oak that makes the barrels comes from Limoges to the east of Charente, and the wood contributes as much as a pound of extract to every 100 litres of aged spirit.

These spirits are housed in the huge warehouses on the banks of the Charente, where the barrels sit quietly ageing, adding colour and texture to the spirits. The evaporation of alcohol through the barrels is continuous - at Hennessy's alone over 700,000 litres of alcohol evaporates into the atmosphere every year - known affectionately as 'the angels' share'.

These eaux de vie are what Cognac is made from. It is almost universally a blend, typically of as many as 100 different eaux de vie. This is why there's never a vintage year on a Cognac whereas there is on an Armagnac, which isn't blended. The blender's art is the final stage in the process, and more on this next week.

Spirit of the Week

Hennessy XO

The most affordable of the fine Cognacs from Hennessy - the next up is Paradis at €220 a bottle and then Richard Hennessy at €1,300 a bottle - by which standards €80 for the XO seems almost a bargain.

The XO is widely available, the others somewhat less so.