John Scharffenberger appears to be slowly but surely working his way through fermented foods, first with sparkling wine, then chocolate, and now sauerkraut.

After a few rounds in his kitchen, trying different types of cabbage and fermenting times, the ever-enterprising Scharffenberger's first batch of high-quality sauerkraut is on the market. An heirloom cabbage variety ("flat Dutch") planted last year, plenty of salt, tanks at Berkeley pickle maker Cultured, and six months' curing time are the sole ingredients. Crunchy, vibrant kraut--full of vitamin C and sinus-clearing pungency--is the refreshingly sour result.

Culture junkies, note: This fermented delight is only available at Let's Be Frank in the Marina. Request some Scharffenberger sauerkraut on your favorite dog at the shop (it goes extremely well with the peppery, pickle-laden Devil Dog sauce), or buy a quart jar ($8) to bring home.

Larry Bain, the mastermind behind Let's Be Frank, uses Sharffenberger's obsessive handiwork to make a ridiculously easy Sauerkraut and Short Rib Soup (click here to download the recipe).

You might think Scharffenberger's next project would be yogurt or vinegar. Instead, he's working on an American version of Spain's famous aged jamóns. But then, what goes better with sauerkraut than a nice bit of pork?

Let's Be Frank, 3318 Steiner St. (at Lombard St.); 415-674-6755 or letsbefrankdogs.com