Vietnamese food is simply cooked but with ingredients as fresh as a daisy.   I have just encountered fresh soy sauce, and it is so different from what I am used to.   Sharper, saltier, altogether more intense and very thin.  It is mostly a dipping sauce and these come in many varieties, adding flavour and texture to many a dish.  Every table is replete with tiny shallow bowls no bigger around than a tiny coffee cup and you are never told what they are.    It is a case of suck it and see.