With crowds clamouring for the delicious shellfish dashi and only five seats to accommodate them, the queue trails out the door and down the street. Hiroyuki Iwata chose basket clams for his broth because his first taste of ramen in this sort of broth was unforgettable. He uses the richly flavoursome clams of Lake Shinji in Shimane Prefecture. To savour the pure taste of the dashi, order the salt ramen. The shop’s name derives from kohakusan (succinic acid), an umami flavour component in shellfish.