Toss the sliced chicken with cornstarch, salt, and pepper.
Mix soy sauce, chicken broth, oyster sauce, sugar, and cornstarch in a small bowl.
Heat oil in a skillet, cook chicken until browned, and set aside.
In the same skillet, stir-fry broccoli until bright green. Add garlic and ginger.
Return chicken to the skillet and add the sauce, stirring until thickened.
Serve hot over rice or noodles.