Combine the peanut butter and sesame oil in a small bowl or measuring cup and stir vigorously with a whisk until well combined; add the rest of the ingredients for the sauce and resume whisking to fully incorporate them; set aside.
Combine the bean sprouts, julienned carrots, bell pepper and snap peas, green onions, cashews and sesame seed in a large mixing bowl; set aside.
Cook the noodles in plenty of salted boiling water until cooked to your liking. As soon as the noodles are cooked, fish them out of the water with a large fork or kitchen tongs and drop them directly in the bowl with the reserved veggies. The heat from the noodles will help wilt the veggies and the starchy water will mix in with the sauce to create the perfect consistency.
Once all the noodles have been added, pour the sauce over them and then delicately toss the salad until well combined.
Technically, you could serve this salad right away, but ideally, you want to cover it and let it sit in the fridge until the next day, or up to a few days; this will allow for the flavors to meld and the veggies to soften.
Take the salad out of the fridge 30 minutes before serving. Leftovers will keep for up to a week.