Bring a large pot of salted water to a boil. Add soba noodles and cook until tender, 6 to 10 minutes (check the package for recommended cook time). Drain and rinse well under cold water.
To make dressing, mix everything in a small mixing bowl and add a little water if sauce is too thick.
To serve place soba noodles in a large serving bowl. Add the rest of the salad ingredients one by one and arrange separately on top of the noodles. Drizzle the dressing over top and garnish with green onions and sesame seeds.