Champagne is one of the most difficult wines to make. Each house makes one that is a blend of vintages.

One might think that this non-vintage (NV) is a catch-all for the wines that are deemed “not good enough” to be vintage champagne (one that is made from a single year’s production) – a way to get rid of the “leftovers” that are lying about in the cellar. In fact, as the brand’s entry-level wine, winemakers see it as an introduction to the house and one that represents the “house style”.

What are the criteria? It must be distinct, consistent and unique. An NV champagne is a marvel because each year, when the wine is blended, it must be similar in style to those released previously.

NV champagne is an “assemblage” – that is, a blend from difference crus. The youngest can be three years old, the oldest from seven to 10 years. It is a test of a cellar master’s talents to recreate the house style and understand how it will taste after spending some time in the bottle.

Dominique Demarville, the cellar master at Veuve Clicquot, was recently in Hong Kong to introduce the champagne house’s Extra Brut Extra Old – an NV combining six different vintages ranging from 1988 to 2010. Many of these were released as vintage champagnes for Veuve Clicquot’s La Grande Dame, and Demarville was curious to find out what they would taste like in a blend of the best.

A Hong Kong sommelier puts her taste buds to the test, with a week in Champagne on the line

One of the best NV champagnes is Krug Grande Cuvée. It is crafted from more than 10 vintages from about 120 lots. A visit to the Krug cellars, in Reims, France, a few years ago gave me a view of its amazing collection of barrels of wine gracefully ageing and waiting to be made into Grande Cuvée. After the champagne is blended, it undergoes further ageing before its release, so in fact, the youngest wine in a bottle of Grande Cuvée will be more than 20 years old by the time the cork is popped.

Another top NV is Laurent-Perrier Grand Siècle. Named for Louis XIV’s era, “the great century”, the bottle is a replica of champagne bottles in the 17th century. It’s an assemblage of the grand crus of the Champagne region – Ambonnay, Avize, Cramant, Chouilly, Mailly, Le Mesnil-sur-Oger and Verzenay. The wines are aged during the second fermentation on the lees (yeast) for about five years.

Tête de cuvée, the best of the best champagne

There’s a way of telling how old an NV champagne is, as some houses now put the date of disgorgement on the bottle. Disgorgement is when the sediment is removed from a bottle of champagne, then a small dosage (sugar in the same wine) is added to bring the volume of liquid in the bottle back up to its stated level, before it is stoppered with a cork.

Krug puts a “Krug ID” on the back of its newer bottles, which allows buyers to check the details of individual bottles using a mobile app.

Alternatively, search on a champagne house’s website or check the QR code.

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At the bottom of the back label on some grower champagnes you may find something like “disgorgement 090828”, meaning August 28, 2009.

Nellie Ming Lee is a food stylist and part-time sommelier studying with the Court of Master Sommeliers