•  How it is made

The theory behind Champagne is simple. Fermentation converts sugar into alcohol and carbonic gas - if the gas is set free the wine is still, if not, it is sparkling. To capture the gas, the wine undergoes a second fermentation in a sealed container. The gas gushes out in the form of tiny bubbles when the container is opened. According to research carried out by Moët & Chandon there are on average 250 million bubbles in a bottle of sparkling wine. The internal pressure in a bottle of sparkling wineis equivalent to the pressure of a double-decker bus tyre.

•  The Grapes Various are used, but Chardonnay and Pinot Noir are best for premium Champagne - they are relatively neutral, with a good balance of sugar and acidity when ripe.

•  Champagne are made by méthode champenoise. As in cuve close, the first fermentation takes place en masse, sometimes in oak barriques, but the second takes place in the actual bottle in which the wine is sold.

•  Some Champagne undergo "malolactic", a natural process of fermentation that converts hard malic acid into soft lactic acid and adds creaminess to the wine. Of the few producers who prevent the malolactic, Bollinger, Alfred Gratien, Krug and Lanson are the most famous.

•  Blending and the Prise de Mousse The blending (assemblage) of the base wine is undertaken after the first fermentation. The champenois are the masters of this, and may create a non-vintage cuvée from as many as 70 base wines. Sugar, selected yeasts, yeast nutrients and a clarifying agent are then added to induce the mousse. The second fermentation is often referred to as the prise de mousse, or "capturing the sparkle", and it can take months to complete. In contract to the first fermentation, which should be relatively fast and warm, the second is slow and cool.

•  Autolysis When the second fermentation is complete, the yeast cells undergo an enzymatic breakdown called autolysis, which is epitomized by an acacia-like flowery freshness. Good autolysis adds complexity and ensures finesse. Remuage and Disgorgement In méthode champenoise only, the yeast deposit created during the second fermentation is encouraged down the neck of the inverted bottle into a small plastic pot held in place by a crown-cap.

•  Remuage (or riddling), as this is called, takes eight weeks by hand, or eight days by machine. The sediment is removed (disgorged) by immersing the bottle in freezing brine, and ejecting the semi-frozen pot without losing too much wine or gas.

•  The Dosage Before corking, the liqueur d'expédition is added. In all cases except extra brut (very dry), this will include some sugar. The younger the wine, the greater the dosage of sugar required. Storing and Serving Sparkling Wine Most fizz is best drunk within a year or so. Only a few cuvées are capable of developing truly complex aromas and flavours after disgorgement. Why Store? Typically, Chardonnay turns "toasty" and Pinot Noir "biscuity", although the reverse in possible

•  What's in a Vintage? A Champagne vintage implies that the harvest was exceptional, vintage Champagne must be 100 per cent from the year, but elsewhere it varies (95 per cent in California ; 85 in Australia ). Store vintage Champagne for 8-10 years from the date of harvest. The term non-vintage (NV) sounds derogatory to many people, but wines from various years can be skilfully blended to create some of the finest cuvées available.