1. Add the chopped chicken, soy sauce, and rice vinegar to a medium-sized mixing bowl or ziplock bag. Coat the chicken in the marinade mixture and allow to marinate for at least 15 minutes to overnight in the refrigerator.
2. As the chicken marinates, add all ingredients for the sauce to a medium bowl. Set aside.
3. Meanwhile, add one to two tablespoons of oil in a large skillet over medium-high heat. Use tongs to remove the chicken from the marinade and transfer directly to the skillet. Reserve the marinade.
4. Cook the chicken for five to seven minutes, or until chicken is nearly cooked through and no longer pink inside.
5. Stir the prepared sauce and pour directly into the skillet with the chicken. Add the reserved marinade (the marinade needs to boil, so be sure this is added at the beginning with the sauce) and bring to a low boil for approximately three minutes. Cook until sauce starts to thicken. Season to taste.
6. Serve garnished with chopped green onions, sesame seeds, or fresh lemon, if desired.