Grind the roasted sesame seeds in a food grinder. Grind until mostly fine but still a little textured — reserve a pinch for garnish.
Bring about 3 quarts water to a boil. Add salt, then add the spinach and blanch just until wilted (about 30–60 seconds), stirring occasionally.
Immediately drain and cool under cold running water (or in an ice bath) to stop cooking.
Squeeze out excess water gently – use your hands first, then wrap in a kitchen paper and squeeze again) Do not smash the spinach!
Cut the spinach into bite-size pieces (about 1 inch long), then loosen the pieces using your hand so they’re not clumped together.
In a medium-sized mixing bowl, combine soy sauce and maple syrup. Mix well.
Add the spinach in the bowl until evenly coated
Sprinkle the ground sesame over the spinach and toss again until evenly coated.
Transfer to a serving dish and sprinkle with the reserved sesame. Served chilled or at room temperature