Bring a stockpot of water to a boil. Stir in noodles, and cook until al dente, about 6 minutes, or according to package instructions. Remove from heat, and drain. Transfer noodles to a serving bowl, and toss with 1 tablespoon sesame oil. Set aside.
Gently toast unhulled sesame seeds in a small skillet set over low heat until just fragrant, about 2 minutes. Transfer seeds to a bowl to cool.
Place toasted sesame seeds, soy sauce, mirin, the remaining 2 tablespoons sesame oil, and the rice-wine vinegar in the jar of a blender; process until smooth and creamy. Pour dressing over reserved noodles, and toss to combine. Sprinkle with black sesame seeds, if using, and scallions. Serve immediately.