Bring a pot of water to a boil. Add noodles and cook 5 minutes, or until tender. Drain and set aside.
In the meantime, whisk together peanut butter, rice vinegar, soy sauce, garlic, ginger, and water in a large bowl. If the sauce is too thick, add another tablespoon of water and whisk again.
Transfer noodles and steamed edamame to the bowl and stir in spinach.
Transfer to a serving dish and garnish with fresh herbs, peanuts, lime wedges, and chili pepper if desired.
