Toss the chicken thigh pieces, cornstarch, salt and pepper in a medium bowl.
Heat 2 tablespoon oil over medium high heat in a large skillet.
Cook chicken in 2 batches turning until golden brown on all sides. Add the remaining oil for the second batch. Remove chicken to a plate and set aside.
Cook vegetables in the same pan until tender-crisp (about 5 minutes).
While vegetables are cooking, mix remaining ingredients in a small bowl.
When vegetables are cooked, add the sauce to the pan and bring to a boil. Lower heat and add chicken back to the pan.
Stir gently until sauce is thickened and coats chicken, about 3 minutes.
Serve over rice and garnish with green onions and sesame seeds.
Notes
Any vegetables may be substituted
Dried ginger may be substituted for fresh
Red pepper flakes can be adjusted for heat preference