Blanch the spinach for a few minutes in boiling water, leaving it tied together, then plunge into ice water to stop it cooking. Drain.

In a shallow dish, combine the dashi and soy sauce.

Squeeze the extra water from the spinach, then remove the strings holding them together and place them in the dashi marinade. Let them sit at room temperature for at least 30 minutes. (She says you can also refrigerate for 2 days, covered.)

Cut into small bundles of 1" length and top with something... I used the furikake. She suggests roasted white sesame seeds or a few other things.