Prep Chicken & Sauce: Cut chicken into bite sized pieces and add to a large bowl. Toss with salt, pepper & ginger, soy sauce & rice vinegar. Toss to coat while you prepare everything else. Beat 2 egg whites in a small bowl and set aside. Mince garlic for sauce and set aside. Cut broccoli & begin to make rice if you are. Slice scallions thin.
Make Sesame Sauce: In a small sauce pan, heat 1tbs sesame oil. When oil is hot, add minced garlic & cook until garlic is fragrant and beginning to get golden. Turn heat to very low. Add all other sauce ingredients (excluding cornstarch). Scrape to make sure sugars are out of bowl. Stir in sauce pan until sugar dissolves and simmer 15 minutes on low while cooking chicken. In a small dish mix cornstarch with a splash of water. Add to sauce when chicken is almost ready. Bring to medium & look for slow, fat bubbles after about 1 minute. Add 1tbs sesame seeds & half of the thin sliced scallions. Stir & set aside.
Coat Chicken: Heat large skillet with avocado oil. Drain chicken of marinade the best you can. Next, add egg whites to chicken and toss to coat really well. Drain again. I like to leave a little in there for the corn starch to stick & extra crispy bits. Add ⅓ cup of cornstarch and toss chicken to coat. It's going to be a little sticky. Toss again in another ⅓ cup cornstarch. Add a splash of water if it seems too dry or there is a lot of unmixed cornstarch.
Make Broccoli: In a large microwave safe bowl, add chopped broccoli, salt & pepper. Microwave to steam for 3-5 minutes. Toss in sauce with chicken.
Make Chicken: When oil is hot enough (chicken sizzles as soon as it hits the oil), add chicken pieces in one layer not touching. Cook 2-3 minutes on one side until nice and golden brown. Flip and cook another 2 minutes. Drain on double lined paper towels. In a large bowl, add all chicken pieces & broccoli and toss to coat. Serve over rice with more sesame seeds and green onion.