Cut the chicken into bite sized pieces and put into a medium sized mixing bowl. Sprinkle and lightly coat with 2 tablespoons of the corn starch.
Heat the olive oil in a large frying pan over medium high heat and add the chicken in a single layer. Saute for about 4 to 5 minutes or until chicken is golden and cooked through. Remove chicken from the pan and set on a plate lined with a paper towel.
Add green beans to the pan and cook for 4 minutes or until tender, stirring occasionally. Remove green beans from pan and set with the chicken.
Pour soy sauce into the pan, along with the sesame oil, garlic, ground ginger, salt, and pepper. Stir the sauce and bring to a boil (1-2 minutes). Mix the remaining corn starch with 2 to 3 tablespoons of water and add to the pan. Whisk the sauce and cook for a few minutes until slightly thickened.
Transfer the chicken and green beans to the pan, mix and wait another 2-3 minutes. Then turn off the heat and leave the dish covered for another 5 minutes. Sprinkle with green onions and sesame seeds before serving.