Mix sauce ingredients in a small pan on medium heat. Stir until gently simmering. Then add cornstarch slurry. Stir until thickened, set aside.
Season chicken with salt & pepper. Heat a large wok or deep skillet over med-high heat and spray with olive oil spray.
Add seasoned chicken pieces and cook for 6-8 min, until golden brown and cooked through. Add minced garlic to hot pan and stir-fry for 30 sec. Set aside.
In the same pan, re-spray if needed. Add julienned carrots and sliced celery. Stir-fry for 2-3 min.
Add mung bean sprouts to the vegetables and stir-fry for another min.
Add udon noodles to the pan. Add ¼ cup of water to loosen them up. Gently separate them if they're stuck together. Stir-fry for 2-3 min until they're heated through.
Return cooked chicken to the pan.
Pour sauce over the noodle mixture.
Toss everything together and cook for 2-3 minutes, until evenly coated.
Taste and season with additional salt and pepper if needed.
