+1 for Bollinger, but as Ryan mentioned above, the Special Cuvée can be quite crisp and citrus-driven in its youth. The toasty darker-toned elements usually start to emerge after a year or two in a cellar.
And Rob, just like you said in your first post: yes, more Pinot Noir / Meunier, less Chardonnay. The toasty / bready / nutty elements come from three different things: yeast autolysis, oxidation and oak. With long aging on the lees a producer increases the time autolyzed yeast elements can incorporate to the wine, bringing in flavors of yeast, bread, toast and brioche. By aging the wine in oak or cellaring the bottle, one slowly introduces oxygen to the wine, bringing in elements of nuts, caramel and toast. Finally, a producer can age wines in smaller and newer barrels, incorporating not just oxygen but also oak flavors into the wine, which tend to hover in the flavor spectrum of oxidation and autolysis, boosting them much more to the fore.
Why Pinot Noir / Meunier? Well, the red varieties tend to have lower acidity and higher pH than Chardonnay, so they oxidize more readily. That means that they don’t tend to make that long-lived wines, but on the other hand, they start to develop those complex oxidative flavors much younger than a 100% Chardonnay.
You mentioned Charles Heidsieck. They don’t use any oak, but they do blend a huge proportion of reserve wines into their cuvées (more oxidative material) and age them very long periods on the lees (lots of autolysis).
Bollinger uses quite a bit of reserve wines, but not as much as Charles Heidsieck. However, they use a very large proportion of Pinot Noir and Pinot Meunier in their wines and age them partially in oak (more oxidative style). The NV tends to be still quite fresh when released, but reaches a more evolved stage much faster than a similar NV Champagne that hasn’t seen any oak and has a bigger proportion of Chardonnay. Furthermore, I think that Bollinger has toned down their sulfites program, which might make the wines come across as developed even faster.
Bollinger’s La Grande Années are aged completely in oak and are made from the best Pinot-driven material they have, so they are pretty much like Special Cuvée on steroids and due to their prolonged aging on the lees they tend to be pretty impressive upon release.
You might also want to check producers from the Aube region, because +90% of the production there is Pinot Noir. That means most of the stuff sees very little if any Chardonnay.
Also producers such as Henri Giraud and Marguet tend to use quite a bit of Pinot Noir and favor oak over stainless steel in their vinification process.
