Cut chicken into bite sized pieces and add to mixing bowl or resealable plastic bag.
Add ingredients for marinade and mix with chicken until combined. Let sit for 15-30 minutes. (This is the preferred method, but if you are short on time, skip the sitting time)
Add 1/2 cup cornstarch to chicken mixture and gently stir until chicken is coated. (Pieces will be sticking together and you can separate during cooking).
Heat vegetable oil in skillet until hot and slightly smoking. Add chicken and separate pieces with spatula or tongs.
Cook without moving the chicken until the bottom is golden brown, about 4-5 minutes. Flip to brown the other side, 2-3 minutes. Remove chicken and set aside. Let cool for 2 to 3 minutes.
While chicken is cooling, add 1 tbsp minced garlic to skillet and let cook 1-2 minutes.
Add sauce mixture and stir in skillet until it is thickened. This happens quickly so don't step away.
Once sauce is thickened, add chicken back and stir to coat chicken with sauce.
Optional: Top with sesame seeds, green onion, red pepper flakes or extra orange zest.