Boil a pot of water and blanch the spinach for about 1 minute. Quickly transfer it to a bowl of ice water to halt the cooking. Drain and squeeze out any excess water.
In a dry skillet over medium heat, toast the sesame seeds until they turn golden and fragrant, stirring often to avoid burning. Remove from heat and let cool.
In a small bowl, mix together the soy sauce, rice vinegar, sugar, sesame oil, minced garlic, grated ginger, and a pinch of salt until the sugar dissolves.
Place the blanched spinach in a serving bowl, drizzle the sesame dressing over it, and gently toss to combine.
Just before serving, sprinkle the toasted sesame seeds on top of the salad.