Add all sauce ingredients to a high-speed blender and blend until combined. Set aside.
Toss chopped veggies, rice noodles, cilantro, and sesame seeds into a medium mixing bowl. Add in chicken if using. Pour in sauce and mix well. Taste and adjust seasoning as needed.
Serve cold topped with protein, scallions, and peanuts if adding.
Store: Leftovers will last in an airtight container in the fridge for up to 4 days. Keep in mind that the noodles will absorb the sauce as it sits, so the leftovers may be a bit dry. If you want to give it a refresh, whip up some extra sauce to add later on! Add an extra squeeze of fresh lime juice, too!