Sadly, that’s only possible in those cases where a wine cites butter as a primary flavor, as in JaM’s Butter. Most of the time, though, experience with a producer is the best guide. And even so, people will perceive wines in different ways, as with the Crowley.
How does that flavor get in the wine? Several people pointed erroneously to oak barrels as the butter culprit. Oak, depending on how it is managed, has its pluses and minuses. But directly causing a buttery flavor is not among them.
If you don’t mind me getting technical, the butter sensation is rather a byproduct of malolactic fermentation, a process that occurs when bacteria transform sharp malic acid in the wine into softer lactic acid. Lactic acid, as the name suggests, is found in dairy products like milk and butter.
When managed properly, the buttery byproduct, or diacetyl, is not particularly noticeable. But, as in the early days of modern California chardonnay, malolactic fermentation can be mismanaged. One result is an abundance of diacetyl, which in Burgundy, the home of chardonnay, was considered a fault.
California winemakers might have considered it a fault, too, except that critics in the 1980s often praised the flavor of butter in chardonnay, and many people grew to like it. What had once been accidental was now intentional.
New oak barrels, or, in the case of cheap wines, oak adjuncts steeped in the wine, like chips, staves or dust, can amplify the buttery quality by adding sweet vanilla flavors. Those flavors can appear in chardonnays that have no trace of butter.
But properly managed, oak barrels are important tools that don’t necessarily add any overt flavors to wine. Rather, they can enhance the texture of a wine, as the barrels are slightly porous, permitting minute amounts of air to pass through.