In a medium bowl, whisk together all of the sauce ingredients (reserving 1 tbsp of orange zest for the end). Set aside.
In a medium-sized skillet, heat 1 tbsp of olive oil over medium-high heat. Add the broccoli, red bell pepper, and onion. Cook the veggies for a minute or two, then turn the heat to medium-low and cover with a lid. Let the veggies finish cooking while you cook the chicken and sauce. You want the veggies to be tender-crisp.
Combine the chicken pieces with 2 tbsp of cornstarch and stir until all of the pieces are coated. Heat 2 tbsp of olive oil in a large skillet over high heat. Add the chicken and season with a little salt and pepper.
Let the chicken cook for a couple of undisturbed minutes before stirring. You want the chicken to crisp up and brown while cooking through.
Once the chicken is cooked, remove to a plate. Lower the heat to medium and add the sauce to the skillet. Let the sauce bubble and cook for a minute or two. It should thicken up a little as well.
Now add the chicken and the veggies back to the skillet and toss them in the sauce until coated.
Serve over white rice and top with sesame seeds, some of the reserved orange zest, and sliced green onions. Enjoy!