Garlic breath is worth it in the name of this flavorful and healthy weeknight dinner. Slideshow: More Stir Fry Recipes
In a small bowl, whisk together the chicken stock, soy sauce, sesame oil, lemon juice, crushed red pepper, black pepper and cornstarch. Set aside.
In a large skillet, heat 2 tablespoons of the olive oil. Add the chicken and stir-fry over moderately high heat until no longer pink and cooked through, about 5 to 7 minutes. Transfer the chicken to a plate.
Heat the remaining 2 tablespoons of oil in the skillet. Add the onion and cook for 3 minutes, then add the garlic and cook for 1 minute, stirring. Add the broccoli and stir-fry until crisp-tender, about 3 to 5 minutes.
Stir the chicken stock mixture into the skillet and cook, stirring, until thickened, about 1 to 2 minutes. Stir in the chicken and cook until heated through, about 1 to 2 more minutes. Season with additional soy sauce if desired.
Garnish with toasted sesame seeds and serve with rice.