Octopus

The king of stubborn collagen. To break its fibers without turning it to mush, two physicochemical schools of thought clash: repeated thermal shock (dipping the tentacles three times in boiling water before immersion) or prior freezing (the formation of ice crystals tears the muscle fibers). Its cooking then requires a long, gentle boil (collagen hydrolysis) or sous-vide cooking. Once tenderized, the finish requires a pass over a white-hot grill to char the suckers and provide a smoky crunch.