Image credit to: Joy Huang
Bring a pot of water to a boil. In the meantime, roll up the kelp and slice into thin ribbons, about 4" long. Combine the soy sauce, rice vinegar, sesame oil, mirin (or sugar), and chopped scallions in a small bowl, reserving 1/4 for the tofu.
Blanch the seaweed in the boiling water for 2 minutes. The seaweed will turn from dark brown to green. Drain and toss with the soy sauce dressing. Marinate for at least 30 minutes in the refrigerator.
When ready to serve, place the tofu on top of the seaweed and pour the rest of the dressing on top. Garnish with more scallions and toasted sesame seeds.