Step 1Combine the lettuces and herbs in a shallow bowl and toss until very well mixed. Add the edamame and toss again.
Step 2In a small bowl, whisk together the mustard, vinegar and sea salt. Whisk in the olive oil until emulsified. Season with pepper to taste.
Step 3Pour the dressing over the greens and toss until coated. Divide among small salad plates and serve at once.