Bring a saucepan of salted water to a gentle boil.
Add soba noodles and cook according to package directions (usually 4–5 min).
During the last 3 min, add broccoli florets and frozen edamame to the boiling water.
Drain noodles, broccoli, and edamame together in a colander; rinse briefly under cool water to stop cooking and preserve color.
Meanwhile, in a mixing bowl whisk together sesame oil, tahini, soy sauce, lemon juice, grated ginger, and minced garlic until smooth and creamy.
Transfer drained noodles, broccoli, and edamame back to the saucepan or a large bowl. Pour the dressing over and toss gently to coat.
Fold in sliced spring onions and adjust seasoning (add a splash more soy or lemon if needed).
Divide into three bowls and top with optional nori strips.