Dry-fry the sesame seeds.Set aside one teaspoonful, then grind the rest into a paste using a pestle & mortar. Mix this paste with the soy sauce, dashi and sugar. Set aside.
Wash and drain the spinach.
Heat the oil, and add a handful of spinach, stir. When it's just wilted, add the second handful. Continue until all spinach is used up. But be careful not to overcook the spinach!
Put the sautéed spinach into a sieve and, using a spoon, squeeze out the liquid, then transfer it to a serving dish.
Add the sauce and sprinkle the sesame seeds on top.