This month, in the midst of a record-breaking heat wave, I met Don Feinberg, who was in Atlanta to showcase some truly unique Belgian beers.

Feinberg is founder of Vanberg & DeWulf, one of the most respected importers of traditional Belgian beers in the United States. And what he had to share turned out to be two very rare kegs of lambic from the Boon Brewery in Lembeek, near Brussels.

Boon Brouwerij, Belgium (ENLARGE)

Frank Boon (right) samples a 2004 vintage cask of Boon lambic.

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Lambic is the oldest (and in many ways most difficult) style of Belgian beer. Brewed with malted barley, wheat and aged hops, "spontaneously" fermented with wild yeast and aged in casks, it has flavors that can range from chardonnay to single malt scotch.

Frank Boon has become well-known as a revivalist of traditional lambic. And his brewery regularly produces most of the variations on the style: geuze (blended lambic), kriek (lambic flavored with fresh cherries), framboise (lambic flavored with fresh raspberries) and faro (lambic sweetened with candy sugar).

Each of the Boon kegs Feinberg presented contained a different noncarbonated, 3-year-old lambic that had been aged in an oak cask. Feinberg first invited tasters to try each one separately. And then, in a third glass, we were instructed to mix the two lambics, deciding on a ratio that we enjoyed in order to concoct our own blend.

The result was remarkable for several reasons. But it was also a real treat because it's virtually impossible to taste this kind of Belgian "base," single cask, "still" lambic in the United States.

"In a nutshell, we were actually pretending that we were geuze blenders," Feinberg said later.

Of course, blending different lambics to make geuze is one of the great arts of Belgian brewing — and one that Boon certainly excels in. Feinberg, who has been importing and promoting Boon's beers since the late 1980s, describes the brewer as an exacting autodidact who has his own take on the lambic style.

"Frank is self-taught but very detail-oriented," said Feinberg. "And his whole mantra is that true, authentic lambic is not supposed to be acidic. It's what he calls superattenuated — meaning it's like dry sherry. It's supposed to be superdry, to the point where you may have an acidic tingle but you don't have a lot of actual acidic acid."

In that sense, Boon has struck a middle ground between the major Belgian lambic producers. On one side are the very sweet-style lambics from Lindemans, which have become the most popular in the United States. And on the other side are the very sour-style lambics from Cantillon, which are somewhat harder to find.

But as Feinberg said, the proof is in the tasting. And even tasting lambic can be rather confusing, especially if you don't quite grasp what has gone into creating all the wonderfully complex flavors and aromas.

Of the two kegs, I leaned toward the first one (from Cask 17B), which Boon described in his notes as having "a very nice woody character, with cloves, vanilla and typical whiskey lactone." The second keg (from Cask 52) had more intensity, which Boon described in terms of "more volatile acids" and more complexity.

The winning blend Feinberg helped me settle on used roughly 60 percent of the second keg for structure and dryness and 40 percent of the first keg for flavor and roundness. Perhaps the most surprising thing was that, despite its lack of fizz, the combo proved quite refreshing on such a hot day.

"That third taste is what makes lambics exciting," Feinberg said, "because that's the real art of making lambics, to create your style and house character."

For a taste of Frank Boon's art, try a bottle of one of his carbonated Marriage Parfait vintage geuze-style lambics, blended from the best casks from outstanding years. His other styles, including kriek and framboise, are also available at several beverage stores and beer bars around Atlanta.