A bottle of concentrated tsuyu sauce with added bonito flakes for a deeper richer flavour tsuyu is the delicious soup stock used for most japanese noodle dishes hotpots and can even be used as a rich dipping sauce for tempura tsuyu has become an increasingly popular condiment in japan and is made from a blend of dashi soup stock and a mixture of soy sauce mirin and sugar use this concentrated tsuyu sauce as a dipping sauce or soup in which to enjoy your somen soba or udon noodles this so