FOR THE CHICKEN STOCK MIXTURE: In a small bowl, whisk together chicken stock, oyster sauce, vinegar, ginger, garlic and Sriracha, if using; set aside.
Season chicken with ½ teaspoon salt and ¼ teaspoon pepper.
In a medium bowl, combine chicken and cornstarch.
Heat canola oil and sesame oil in a large skillet over medium high heat.
Working in batches, add chicken to the skillet in a single layer and cook until golden brown, about 7-8 minutes.
Stir in broccoli and CHICKEN STOCK MIXTURE until broccoli is just tender, about 3-4 minutes.
Serve immediately, garnished with sesame seeds.
