One of the most exciting developments in beer this year is that sour beers, once neglected like documentaries in a Blockbuster, started popping up at beer bars everywhere — on tap. In my beer-nerd training days, drinking my first sour beer was a big step that took years to lead up to, in part because they’re as expensive as they are shockingly different. Now, you can walk into good bars in D.C. and find sour-beer converts that only a month ago were chugging Blue Moon.

Huge credit goes to the merchants who carry these beers, who respect their clientele enough to challenge their palates and not bother with the fizzy yellow stuff. But it also helps that this year marked the debut of one of the world’s finest sour beers, Cuvee des Jacobins Rouge, by Belgium’s Bockor. (The link says Ommegang; I’ll explain.) Rouges, or Flemish red ales, are light, sweet-tart beers that pick up sourness by aging in oak barrels — during which time wild yeast lingering in the barrels (or permeating through the wood) make themselves cozy in the beer and impart all kinds of weird flavors. Though some Flemish reds get downright saccharine, the red color comes from red malts, not fruit juice or, I dunno, Red #40.

Anyway. Cuvee des Jacobins has lush notes of black cherry, but it’s far too puckery to be even called sweet. That’s because whereas most Flemish reds are a blend of oak-aged beer and “young” beer, Cuvee des Jacobins is 100% oak-aged, and for a whopping 18 months. That’s why it tastes a little like licking furniture — and believe me, it’s a wonderful thing.

“How wonderful is it?” you ask. “Wonderful enough to be in your Top 5 Beers of 2009, which comes out on Young & Hungry tomorrow?” Maybe, my son. Maybe.

Final note: This new beer originated as Ommegang Rouge, which came out for a limited time this summer — though Bockor produced the beer, it was originally created for Ommegang, to Ommegang’s specifications. For summer 2010, Ommegang is planning a similar collaboration with Liefmans, a standard-bearer for Flemish brown ales. And this is exciting, very exciting indeed.