A side dish of blanched spinach and sliced shiitake mushrooms tossed with ground roasted sesame seeds, dashi, Japanese soy sauce, mirin, sugar and sesame oil.
Rinse the spinach well. If the stalks are rather large and tough, pick the leaves and discard the stalks. Otherwise, include the stalks in the dish and just roughly chop everything.
Boil water in a large pot and add a teaspoon of salt. Blanch the spinach for about a minute. Scoop out and drain (keep the water in the pot boiling).
Dump the spinach in a bowl of iced water. Drain. Squeeze out as much water as you can. Place in a bowl and set aside.
Dump the sliced shiitake in the boiling water, cook for a minute, drain well and toss with the cooled spinach.
Make the sesame dressing (goma-ae)
Dry toast the sesame seeds in a pan until nutty in aroma and glistening.
While the seeds are hot, grind using a suribachi (a regular mortar and pestle will do but will require a longer time to grind).
Transfer a quarter of the ground sesame seeds to a bowl and reserve.
To the remaining sesame seeds in the grinder, add the rice vinegar, dashi, soy sauce, mirin and sugar. Stir to dissolve the sugar and blend the flavors.
Assemble the salad
Pour a tablespoon the dressing on the spinach and shiitake. Toss. Taste. Depending on how much spinach you have, you may need more than a tablespoonful of dressing. So, add more dressing, if needed.
Drizzle some sesame oil, if using, and don't overdo it, and toss a few more times.