This delicate soup, called O-sumashi, which is often eaten with sushi, is very quick to make if you prepare the first dashi beforehand or if you use freeze-dried dashi-no-moto.
Ingredients
4 mitsuba sprigs or 4chives and a fewsprigs of mustard and cress
Mitsuba leaves are normally sold with the stems and roots on to retain freshness. Cut off the root, then cut 5cm/2in from the top, retaining both the long straw-like stem and the leaf.
Blanch the stems in hot water from the kettle. If you use chives, choose them at least 10cm/4in in length and blanch them, too.