In the heart of the Champagne region, just south of Épernay, there is a ridge line of chalky slope called the Côte des Blancs, which has the perfect growing conditions for Chardonnay grapes destined for secondary fermentation. The village of Avize is a Grand Cru of the region within a region. But, while many of the famous Champagne houses have parcels of vineyard there, Frerejean Frères actually does its winemaking here, just yards from its own vines.

The Frères themselves – Guillaume, Richard and Rodolphe Frerejean-Taittinger – spent much of their childhood around Avize. They are part of the family associated with the better-known Champagne house, but on their father’s side, they are descended from the brothers George and Louis Frerejean, cannon-makers to Louis XVI, to the government of the Revolution and to Napoleon – a pretty impressive political agility. Another ancestor is Gavriil Golovkin, Peter the Great’s right-hand man and someone who knew a thing or two about fine wines and hospitality.

In 2005, in the brief period when the Taittinger group was sold to Starwood, before being bought back a year later by Pierre-Emmanuel Taittinger – minus the hotels it had previously owned – the three brothers decided not to throw the small number of vineyards they personally owned into the pot, but start a grower champagne business with the potential to become a house. (Their late uncle Claude Taittinger told them it takes 20 years to build a champagne house – so they are close.)

Growing their own grapes, mostly within sight of their childhood home, means that chardonnay dominates their winemaking. Even the extra brut is a 50/50 blend of pinot noir and chardonnay. And it is in their blancs de blancs that the exceptional character of those grapes is given full expression, thanks to winemaker Didier Pierson. One of his rules is that grapes must be hand-selected and cut from the vine, rather than sorted later. Another is to age his Champagnes for a minimum of six years.

The “basic” blanc de blancs (£65) is a wonderfully complex expression – nutty, briochey depth with tropical and citrus notes pinging off the top. But it is in the Cuvée des Hussards where the detailed minerality comes to the fore – most of all in the newly released Cuvée des Hussards 2008 Deep Sea Aged, which spent 12 months of its eight-year maturation in a cage 60m below the waves off the coast of Brittany.

Undersea ageing is a relatively new trend among Champagne makers. The dark and cold of the sea bed is similar to that of the chalk crayères of Champagne, while the gentle undulation of currents and undertows mimics the riddling process. The unique benefit is supposed to be caused by the fact that the pressure outside and inside the bottle equalises at 60m below; this slows certain aspects of the ageing process, so the Champagne develops complexity but maintains freshness and minerality.

Certainly the result, in the case of FJF’s Deep Sea Aged 100% Chardonnay, carries iodine and other maritime notes to the nose. How much of that is psychologically induced by clutching the remarkable barnacle-clad bottle is up for debate, but this is a champagne that has plenty of creamy maturity and roundness without losing any of the fresh zing of youth.

Champagne Frerejean Frères 2008 Cuvée des Hussards Deep Sea Aged is available exclusively at Harrods; 70cl, £825.