Prepare Chicken: Cut up chicken into about inch size pieces. Season the chicken pieces with salt and pepper.
Make the Sauce: In a bowl, whisk the soy sauce, water, mirin, brown sugar, honey, garlic, and ginger. Pour 1/4 cup of the teriyaki sauce over the chicken and toss to coat. Cover and let marinate for at least 15 minutes in the fridge.
Heat the oil in a large wok or skillet over medium-high heat. Add the chicken and stir-fry until browned and cooked through, about 5 minutes. Transfer to a plate.
Add more oil if necessary, toss in onions and saute. Let them cook for about 2-3 minutes then add in the broccoli (and any other veggies). Cook until everything is tender yet still a little crisp. At the end I added some roasted red peppers.
Pour in the sauce over the veggies. Allow to simmer for a couple minutes. Add the cornstarch slurry while whisking constantly. Continue to simmer, stirring frequently, until the sauce thickens, about 2-3 minutes. Remove from heat and set aside.
While you are cooking the veggies, get the noodles going. Cook the noodles according to package directions until al dente (still some bite, don't want them to be mush). Drain and rinse under cold water, to stop them from cooking.
Add the cooked chicken and noodles to the pan with the veggies. Toss everything and stir-fry for 1-2 minutes until heated through and well combined.
Serve the teriyaki chicken noodles garnished with sliced green onions. Enjoy!