In a medium bowl, whisk together the sauce ingredients: peanut butter, water, honey, soy sauce, red curry paste, vinegar, ginger, garlic, and red pepper ﬂakes until smooth. Set aside.
In a large wok or deep, large nonstick skillet, heat 1 tablespoon of the oil over medium- high heat. Once the oil is hot, add the onion and cook until fragrant and beginning to soften, about 3 minutes.
Add the chicken and sauté, stirring occasionally, until fully cooked through and the juices run clear, about 4 minutes. Remove the chicken and onion from the skillet and set aside.
Add the remaining 1 tablespoon oil, then the mixed vegetables. Sauté until the vegetables are crisp- tender, 3 to 5 minutes, depending on the vegetables selected.
Return the chicken and onion to the skillet. Add the reserved peanut sauce. Toss to coat evenly, and cook until heated through, about 2 minutes.
Stir in the peanuts and cilantro. Serve hot over rice, topped with additional chopped peanuts and cilantro as desired.