In a medium bowl, whisk peanut butter, vinegar, sesame oil, sherry, soy sauce, sriracha and scallions together until smooth. Cover and refrigerate overnight or at least 6 hours. (If it thickens up too much in the fridge, add a bit of water to bring it to the right consistency.).
After the dressing is done chilling in the fridge, bring a pot of water to a boil and cook the rice noodles about 3 minutes, or until tender. (If your package has directions, follow those, but the rice noodles can quickly turn to mush if overcooked) Drain and rinse with cold water. Cut them into about 3-inch pieces and set aside.
In a large bowl, add all your prepared veggies and chicken, then toss. Add in the cooked noodles, and gently combine. Pour the dressing over the top and stir to coat, using as much or little dressing as you'd like. Top with toasted sesame seeds and serve.