Kokotxas are the lower chin of hake or cod; al pil pil they are poached in olive oil until the gelatin binds the sauce, which is made only with cod.
Spanish Wikipedia defines the cococha, from the Basque kokotxa, as the lower part of the chin of hake or cod and says the most common preparations are in salsa verde or al pil pil, the latter only with cod. For pil pil the kokotxas are poached in olive oil until they release their gelatin and the cazuela is moved to make the emulsion. Berton lists kokotxas of cod in pil-pil sauce, and Casa Rufo lists kokotxas de bacalao al pil-pil at 32 euros. Nerua's tasting menu includes a hake kokotxa with pochas beans.
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