Slice the chicken breasts.
In a bowl, add soya sauce, vinegar, salt, black pepper, and garlic powder.
Now add chicken and give it a good mix.
Marinate chicken for 01 hour.
In a pan, add oil (Vegetable/sesame) and heat it up.
Add grated garlic and green chilies.
Saute until it changes color and gets aromatic.
Now add marinated chicken and cook on high heat until the chicken changes its color.
Now add onion and capsicum slices and stir fry with chicken.
Add chicken broth and cover the lid.
Cook for 5 minutes to tender the chicken. (If you are using thick chicken pieces then give it more time to get tender).
In the meanwhile, prepare cornstarch mixture and chicken broth.
Add in chicken after 5 minutes.
Stir quickly and cook for 5 more minutes on low medium heat to settle the chicken sauce thickness.
Now the chicken is ready to serve.