Prepare 2 bowls: one with beaten egg, and another with cornstarch mixed with a pinch of salt and pepper.
Dip the chicken into the beaten egg, then transfer the pieces into the cornstarch and toss to lightly and evenly coat.
Heat 1 tablespoon of oil in a non-stick skillet over medium heat. Add the chicken pieces in a single layer, without overlapping. Cook for about 8–10 minutes, until golden brown on all sides.
In a medium bowl, whisk together all the sauce ingredients. Pour the sauce over the chicken, toss to coat well, then set aside.
Quickly wipe the skillet with a paper towel and add the remaining 1 tablespoon of oil. Preheat the skillet again. Stir fry the broccoli for 2–3 minutes, until it starts to brown. Season with a pinch of salt and pepper, then set aside.
Add about 1/2 cup of cooked quinoa to each meal prep bowl. Divide the chicken and broccoli evenly over the quinoa. Garnish with green onions, sesame seeds, and lime wedges.
Refrigerate the bowls for up to 4 days. Serve cold or reheat as desired.