Brett happens

Crémant de Loire 2004, Extra Brut, Quadrille, Langlois-Chateau ($28.40, 11791670)
A quadrille is an 18th-century dance involving four couples. Here it refers to the four grape varieties used – Chenin Blanc (50%), Chardonnay (30%), Cabernet Franc (15%) and Cabernet Sauvignon (5%) – and the four Saumur vineyards where the grapes are grown. Manually harvested. Pneumatically pressed. Each vineyard’s produce is vinified separately in temperature-controlled vats and subsequently blended. Made using the traditional method. Matured on the lees for four years. The champagne house Bollinger has owned Langlois-Chateau (spelled sans circumflex, TYVM) since 1973. 12.5% ABV.
Initially odd nose – wet dog and honeysuckle – segues into more appealing sour apple and yeast. Clean and bright on the palate. Straightfowardly fruity but very dry. Fine effervesence and crisp acidity lighten the fairly rich texture. Lingering minerals. Well fashioned, even elegant, if a little short on personality. (Buy again? Maybe, though equally interesting and more characterful sparklers can be found for less.)

Champagne grand cru, Blanc de Blancs, Réserve Brut, De Sousa ($69.25, 11797369)
100% Chardonnay from the Avise, Cramant, Le Mesnil sur Oger, Chouilly and Oger grand cru vineyards. A blend of two or three vintages with a minimum of 25% barrel-aged vin de réserve. Made entirely from tête de cuvée juice (the first out of the press). Vinified in temperature-controlled metal vats. Unchaptalized. 12.5% ABV.
Barley sugar, browning apple, hints of buttered toast. Quite rich and full, with faint oxidized fruit and honey notes. The round bubbles provide lift and ripe acidity keeps things taut. Underpinning crystals and chalk add complexity. Long, tasty finish. (Buy again? Maybe, though equally interesting Champagnes can be found for less.)