Steps

• In a medium bowl, combine the cut chicken pieces, soy sauce, toasted sesame oil, cornstarch, and black pepper. Mix well to ensure even coating and marinate for at least 15-20 minutes.
• In a small bowl, whisk together the soy sauce, mirin, oyster sauce, rice vinegar, brown sugar, toasted sesame oil, grated ginger, minced garlic, and red pepper flakes. In another bowl, mix cornstarch with cold water to create a slurry. Set aside.
• If using dried udon, cook according to package instructions until just al dente. If fresh or frozen, cook as necessary according to package instructions.
• Heat neutral cooking oil in a large wok over medium-high heat. Add marinated chicken in a single layer and cook for 3-5 minutes per side until golden brown and cooked through. Remove and set aside.
• Add remaining oil to the wok, then stir-fry onion and white parts of green onion for 2-3 minutes until softened. Add carrots and bell peppers, stir-fry for another 3-4 minutes.
• Add cooked udon noodles and fresh greens to the wok, toss gently for 1-2 minutes until greens begin to wilt. Return the cooked chicken to the wok.
• Pour the stir-fry sauce over the contents of the wok and toss well to coat. Bring to a gentle simmer.
• Add the cornstarch slurry to the simmering sauce and stir for 1-2 minutes until thickened. Serve in bowls and garnish as desired.