In a small bowl, whisk together soy sauce, oyster sauce, rice wine vinegar, brown sugar, ginger, garlic, sesame oil, cornstarch and Sriracha, if using; set aside.
Heat olive oil in a large cast iron skillet over medium high heat. Add shrimp, and cook, stirring occasionally, until pink, about 2-3 minutes.
Add broccoli, and cook, stirring frequently, until tender, about 2-3 minutes.
Stir in soy sauce mixture until well combined and slightly thickened, about 1-2 minutes.
Serve immediately, garnished with green onion and sesame seeds, if desired.
Notes
*24 ounces broccoli florets is equal to about 5 cups.