At this fifth-generation, family-owned brewery, the beer has a not-so-secret ingredient: rocks. Not just any rocks, but hunks of granite heated in a roaring open fire. Once the stones glow dull red, the brewer carefully extracts them from the flames and adds them to 120-year-old granite vats. The white-hot granite caramelizes the malt sugars in the wort, lending a pleasantly toasty flavor to the finished Steinbier (literally “rock beer”). Steinbier is hardly a new invention. Until the end of the 1800s, blazing-hot rocks were an oft-used component of the brewing…