Chop the kale into about 1 inch thick strips and set aside. Slice the onion in half once, then cut into each half so that you get about 1/4 inch thick, half-moon slices and set aside. For the chicken, slice into thin strips of the chicken (Tip: I find that cutting into the chicken at about a 45 degree angle instead of straight up and down cuts makes the meat more tender!)
If you have one, use a wok! If not, get our a large sauté pan. When the wok/pan is hot, add the vegetable or wok oil followed by the chicken. When cooked all the way through, about 4-5 minutes, transfer the chicken to a clean bowl and set aside.
Add the onions with about 1/4 of the sauce and cook for 1-2 minutes or until they start to get translucent. Add the kale and another 1/4 of the sauce and cook down until the kale is bright green in color and soft. Add back in the cooked chicken and the rest of the sauce and stir until the chicken is hot.