Clean and separate green onions into white and green parts.
Chop both white and green parts into 1" sections. If the white part of the green onions is very large around, also slice in half lengthwise.
Dice your chicken breasts into even, bite sized pieces.
Add cornstarch and salt & pepper to plastic bag.
Plunk your chicken into the bag.
Blow a little air into the bag, twist it closed and shake the chicken in the cornstarch.
Fry your coated chicken, the WHITE part of the green onions and garlic over medium/high heat in 1 Tbsp. vegetable oil. You may have to do 2 batches to avoid overcrowding (and therefore steaming) the chicken. Add another Tbsp. of oil if a second batch is needed and remove the first batch to a plate.
Once the chicken, onions and garlic are cooked, return it all to the pan. Add ¼ cup of rice vinegar and cook until evaporated. Add ¼ cup Hoisin Sauce and ¼ cup of water. Cook and stir until fully combined.
Remove from heat and stir in the green bits of the green onion, toasted cashews and oranges.