This Valentine’s Day, forget the Whitman’s Sampler. The ever-adventurous folks at Sam Adams have gone one better, coming up with a confectionary concoction that infuses the robust, dark complexity of a bock with the luscious, semisweet-chocolate aromatics of cocoa beans. Few beers are better suited to soothe your soul on a chilly night of swirling wind and snow.

The bock style is ideal for this time of year — a big, warming beer with a gorgeous ruby-brown complexion. It was developed centuries ago by Bavarian monks to sustain them through abstemious Lenten weeks when eating was verboten but quaffing was sacrosanct.

"This is a true South German bock," says Sam Adams founder Jim Koch, over pints of the stuff at his Jamaica Plain brewery. "A big, malty, more alcoholic, warming rich bock."

With one twist. "I love chocolate," he says. "And I love beer. Both beer and chocolate have extraordinary flavor complexity. And so the idea of putting the two together intrigued me because of the depth and layers of flavor you could imagine from that." Koch points out that chocolate has not always been used almost exclusively as a sweet confection; only in the past century or so has it shown up primarily in candy bars. "It’s a very versatile spice that has been underused," he says. "You’ve got this incredible package [of flavors]: bitter, tart, earthy. It’s got some almond, it’s got mocha, it’s got cherry ... it’s got a lot going on."

Chocolate has shown up in porters and stouts before, but Koch wanted to avoid the "cliché" of a chocolate stout. "I wanted something to bring out the smoothness, the richness, the velvety taste of chocolate, rather than the burnt notes. That’s when the idea of a bock started to make sense."

So he teamed up with Berkeley chocolatiers Scharffen Berger and set about figuring how best it could be done. Almost immediately, they faced two dilemmas. First, in what form do you use the chocolate — when it’s still a raw cocoa bean, or as a processed bar? And at what point in the brewing process do you add it to the beer? In the mill? The mash tub? Kettle? Fermenter? After months of trial and error, Koch and his brewers decided on the best course of action.

"Basically, we aged the [finished] beer on a bed of what are called cocoa nibs. Those are the dried cocoa beans as they come from the farm. And it makes sense, in retrospect. We get the chocolate at the very beginning of the processing, so we’re as close as possible to the essence of the chocolate ... and then we put it in the beer at the end of the process. So it sort of minimizes the processing of it all."

The real richness of chocolate flavor comes from the aroma, Koch explains, and limiting the machinations involved in infusing the beer with the bean maximizes its olfactory impact. As a welcome side effect, the "long, slow, cold infusion" process, which lasts about a month, brings out all the flavor and aromatics of cocoa beans, while adding none of the extra calories of chocolate.

Which is a good thing, because the bock makes a perfect partner for guilty postprandial pleasures like chocolate cake, rich mousse, and mascarpone cheese and fruit — more flavors that meld euphoniously with the mercurial mélange at work in the beer.

"Beer and chocolate are two of the most complex foods or beverages," says Koch. "There’s so much going on in your mouth. It’s like three symphonies playing at once."

Available for about $14.99 for a 750-ml bottle at Kappy’s, Huntington Wine & Spirits, and Martignetti’s, and at Anam Cara in Brookline and Sunset Cantina in Allston.