For the past two years, the Boston Beer Co., maker of Samuel Adams beers, has been working with Germany's Weihenstephan Brewery, the world's oldest brewery, to create an entirely new style of beer. Boston Beer founder Jim Koch and Weihenstephan director Josef Schradler announced this morning that the collaboration is complete.

The new beer, a champagne-like ale called Infinium, will hit store shelves in early December.

The two brewers claim Infinium is the first new beer created under the German beer purity law, called the Reinheitsgebot, in more than 100 years. (Under the law, only four ingredients -- malt, hops, yeast, and water -- can be used to make beer.)

"Frankly it was really cool and a huge honor," Koch told us. "Probably the most important brewery in the old world reached out to Sam Adams. I was like, 'Wait a minute. I was making beer in my kitchen 26 years ago. You guys were making beer a thousand years ago. Why do you need me?' They had an interesting perspective on Sam Adams. They said, 'You're the largest craft brewer in the world.' Well, yeah, I guess, but we're not even 1 percent of the US beer market. In the US, we're pretty trivial."

So what does Infinium taste like? We haven't had a chance to try it yet, but Koch says it's a deep golden, bubbly ale with a fruity aroma and contains 10.3 percent alcohol, more than twice that in a Sam Adams Boston Lager.

"The flavor idiom would be sort of in between a champagne, a dessert wine, and maybe a Sam Adams Noble Pils," Koch said. "You get some of the body and mouthfeel of a beer, some of the hop character of a beer, but it's very dry and acidic without being thin. And then it has some of the fruitiness -- pear, apple, peach, apricot notes -- of a dessert wine."

Sounds tasty. But it doesn't come cheap. The retail price will be $19.99 for a 750-milliliter bottle. Because it's been brewed in both Boston and Germany as a limited release, Koch said he expects most of it to be gone from liquor stores by New Year's Day.

Which raises another question: If this is such an important new beer, why not brew it all the time? "You know, we might," he said. "The thing is, it's quite challenging to make. It goes through a very difficult brewing process that is very time consuming and it ties up the brewery. Maybe someday."