eisbock

a strong German lager in which ice forms in the final stages of secondary fermentation, thus concentrating the alcohol
Found on https://www.encyclo.co.uk/local/20454

Eisbock

Eisbock is an extra-strength style of bock beer. During brewing it is frozen and some of the ice removed to increase the potency. Eisbock was the forerunner of modern ice-beers.
Found on http://www.probertencyclopaedia.com/browse/QE.HTM
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