Preheat a Blackstone Grill over medium high heat.
Place the diced chicken, cornstarch, salt and pepper in a sealed bag. Toss the bag ingredients until the chicken is thoroughly coated in the mixture.
Whisk the sauce ingredients together in a mixing bowl.
Drizzle the oil onto the grill and spread it around with a spatula.
Place the chicken in a single layer on the grill and sauté for 5-6 minutes, tossing it halfway through the cook time, until the chicken is browned and cooked through.
Push the chicken to a cool side of a grill and spread the vegetable out onto the grill in a single layer.
Cook for 2-3 minutes, tossing the vegetables frequently, until the veggies are tender.
Toss the chicken back into the cooked veggies and pour the sauce on top.
Toss to coat the chicken and vegetables with the sauce and cook for 2-3 minutes until the sauce thickens.
Remove from the grill, serve immediately while warm topped with green onions and enjoy!