If using fresh or frozen beans, place them in a pot of boiling water and cook for 3 minutes. Alternatively, steam them over boiling water. Drain and let cool completely.
In a medium bowl, whisk together the soy sauce, mirin, rice vinegar, sesame oil and miso paste until smooth.
Add the cooled edamame to the dressing and toss well to coat. Cut the baked or roasted sweet potato into bite-sized chunks and add to the bowl along with the sliced spring onions. Toss gently to combine.
Sprinkle the salad with toasted sesame seeds for extra crunch and aroma. Serve immediately as a side dish, in a bento box, or as a light, protein-rich main.